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NetBSD 6.1.5 - man page for postconf (netbsd section 5)

POSTCONF(5)									      POSTCONF(5)

NAME
       postconf - Postfix configuration parameters

SYNOPSIS
       postconf parameter ...

       postconf -e "parameter=value" ...

DESCRIPTION
       The Postfix main.cf configuration file specifies a small subset of all the parameters that
       control the operation of the Postfix mail system. Parameters not specified in main.cf  are
       left at their default values.

       The general format of the main.cf file is as follows:

       o      Each  logical  line has the form "parameter = value".  Whitespace around the "=" is
	      ignored, as is whitespace at the end of a logical line.

       o      Empty lines and whitespace-only lines are ignored, as are lines  whose  first  non-
	      whitespace character is a `#'.

       o      A  logical line starts with non-whitespace text. A line that starts with whitespace
	      continues a logical line.

       o      A parameter value may refer to other parameters.

	      o      The expressions "$name", "${name}" or "$(name)" are recursively replaced  by
		     the value of the named parameter.

	      o      The expression "${name?value}" expands to "value" when "$name" is non-empty.
		     This form is supported with Postfix version 2.2 and later.

	      o      The expression "${name:value}" expands to "value"	when  "$name"  is  empty.
		     This form is supported with Postfix version 2.2 and later.

	      o      Specify "$$" to produce a single "$" character.

       o      When the same parameter is defined multiple times, only the last instance is remem-
	      bered.

       o      Otherwise, the order of main.cf parameter definitions does not matter.

       The remainder of this document is a description of all Postfix  configuration  parameters.
       Default	values	are  shown  after the parameter name in parentheses, and can be looked up
       with the "postconf -d" command.

       Note: this is not an invitation to  make  changes  to  Postfix  configuration  parameters.
       Unnecessary changes can impair the operation of the mail system.

2bounce_notice_recipient (default: postmaster)
       The  recipient  of undeliverable mail that cannot be returned to the sender.  This feature
       is enabled with the notify_classes parameter.

access_map_defer_code (default: 450)
       The numerical Postfix SMTP server response code	for  an  access(5)  map  "defer"  action,
       including  "defer_if_permit"  or  "defer_if_reject". Prior to Postfix 2.6, the response is
       hard-coded as "450".

       Do not change this unless you have a complete understanding of RFC 2821.

       This feature is available in Postfix 2.6 and later.

access_map_reject_code (default: 554)
       The numerical Postfix SMTP server response code for an access(5) map "reject" action.

       Do not change this unless you have a complete understanding of RFC 2821.

address_verify_cache_cleanup_interval (default: 12h)
       The amount of time between verify(8) address verification database cleanup runs. This fea-
       ture requires that the database supports the "delete" and "sequence" operators.	Specify a
       zero interval to disable database cleanup.

       After each database cleanup run, the verify(8) daemon logs the number of entries that were
       retained  and  dropped.	A  cleanup  run is logged as "partial" when the daemon terminates
       early after "postfix reload", "postfix stop", or no requests for $max_idle seconds.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.7.

address_verify_default_transport (default: $default_transport)
       Overrides the default_transport parameter setting for address verification probes.

       This feature is available in Postfix 2.1 and later.

address_verify_local_transport (default: $local_transport)
       Overrides the local_transport parameter setting for address verification probes.

       This feature is available in Postfix 2.1 and later.

address_verify_map (default: see postconf -d output)
       Lookup table for persistent address verification status storage.  The table is  maintained
       by the verify(8) service, and is opened before the process releases privileges.

       The lookup table is persistent by default (Postfix 2.7 and later).  Specify an empty table
       name to keep the information in volatile memory which is lost after  "postfix  reload"  or
       "postfix stop". This is the default with Postfix version 2.6 and earlier.

       Specify	a  location  in a file system that will not fill up. If the database becomes cor-
       rupted, the world comes to an end. To recover delete  (NOT:  truncate)  the  file  and  do
       "postfix reload".

       Postfix	daemon	processes  do not use root privileges when opening this file (Postfix 2.5
       and later).  The file must therefore be stored under a Postfix-owned directory such as the
       data_directory.	 As  a	migration  aid,  an  attempt to open the file under a non-Postfix
       directory is redirected to the Postfix-owned data_directory, and a warning is logged.

       Examples:

       address_verify_map = hash:/var/db/postfix/verify
       address_verify_map = btree:/var/db/postfix/verify

       This feature is available in Postfix 2.1 and later.

address_verify_negative_cache (default: yes)
       Enable caching of failed  address  verification	probe  results.   When	this  feature  is
       enabled, the cache may pollute quickly with garbage.  When this feature is disabled, Post-
       fix will generate an address probe for every lookup.

       This feature is available in Postfix 2.1 and later.

address_verify_negative_expire_time (default: 3d)
       The time after which a failed probe expires from the address verification cache.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.1 and later.

address_verify_negative_refresh_time (default: 3h)
       The time after which a failed address verification probe needs to be refreshed.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.1 and later.

address_verify_poll_count (default: normal: 3, overload: 1)
       How many times to query the verify(8) service for the completion of an  address	verifica-
       tion request in progress.

       By  default,  the  Postfix SMTP server polls the verify(8) service up to three times under
       non-overload conditions, and only once when under overload.  With Postfix version 2.5  and
       earlier, the SMTP server always polls the verify(8) service up to three times by default.

       Specify 1 to implement a crude form of greylisting, that is, always defer the first deliv-
       ery request for a new address.

       Examples:

       # Postfix <= 2.6 default
       address_verify_poll_count = 3
       # Poor man's greylisting
       address_verify_poll_count = 1

       This feature is available in Postfix 2.1 and later.

address_verify_poll_delay (default: 3s)
       The delay between queries for  the  completion  of  an  address	verification  request  in
       progress.

       The default polling delay is 3 seconds.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.1 and later.

address_verify_positive_expire_time (default: 31d)
       The time after which a successful probe expires from the address verification cache.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.1 and later.

address_verify_positive_refresh_time (default: 7d)
       The  time  after which a successful address verification probe needs to be refreshed.  The
       address verification status is not updated when the probe fails (optimistic caching).

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.1 and later.

address_verify_relay_transport (default: $relay_transport)
       Overrides the relay_transport parameter setting for address verification probes.

       This feature is available in Postfix 2.1 and later.

address_verify_relayhost (default: $relayhost)
       Overrides the relayhost parameter setting for address verification probes.  This  informa-
       tion can be overruled with the transport(5) table.

       This feature is available in Postfix 2.1 and later.

address_verify_sender (default: $double_bounce_sender)
       The sender address to use in address verification probes; prior to Postfix 2.5 the default
       was "postmaster". To avoid problems with address probes	that  are  sent  in  response  to
       address	probes,  the Postfix SMTP server excludes the probe sender address from all SMTPD
       access blocks.

       Specify an empty value (address_verify_sender =) or <> if you want to use the null  sender
       address.  Beware,  some	sites  reject  mail  from  <>, even though RFCs require that such
       addresses be accepted.

       Examples:

       address_verify_sender = <>
       address_verify_sender = postmaster@my.domain

       This feature is available in Postfix 2.1 and later.

address_verify_sender_dependent_default_transport_maps (default: $sender_dependent_default_trans-
       port_maps)
       Overrides  the sender_dependent_default_transport_maps parameter setting for address veri-
       fication probes.

       This feature is available in Postfix 2.7 and later.

address_verify_sender_dependent_relayhost_maps (default: $sender_dependent_relayhost_maps)
       Overrides the sender_dependent_relayhost_maps parameter setting for  address  verification
       probes.

       This feature is available in Postfix 2.3 and later.

address_verify_service_name (default: verify)
       The  name of the verify(8) address verification service. This service maintains the status
       of sender and/or recipient address verification probes, and generates probes on request by
       other Postfix processes.

address_verify_transport_maps (default: $transport_maps)
       Overrides the transport_maps parameter setting for address verification probes.

       This feature is available in Postfix 2.1 and later.

address_verify_virtual_transport (default: $virtual_transport)
       Overrides the virtual_transport parameter setting for address verification probes.

       This feature is available in Postfix 2.1 and later.

alias_database (default: see postconf -d output)
       The  alias  databases  for  local(8)  delivery  that are updated with "newaliases" or with
       "sendmail -bi".

       This is a separate configuration parameter because  not	all  the  tables  specified  with
       $alias_maps have to be local files.

       Examples:

       alias_database = hash:/etc/aliases
       alias_database = hash:/etc/mail/aliases

alias_maps (default: see postconf -d output)
       The  alias  databases  that  are  used  for  local(8)  delivery. See aliases(5) for syntax
       details.

       The default list is system dependent.  On systems with NIS, the default is to  search  the
       local alias database, then the NIS alias database.

       If  you	change	the alias database, run "postalias /etc/aliases" (or wherever your system
       stores the mail alias file), or simply run "newaliases" to build the necessary DBM  or  DB
       file.

       The  local(8)  delivery	agent  disallows  regular  expression  substitution of $1 etc. in
       alias_maps, because that would open a security hole.

       The local(8) delivery agent will silently ignore requests to use  the  proxymap(8)  server
       within  alias_maps.  Instead  it will open the table directly. Before Postfix version 2.2,
       the local(8) delivery agent will terminate with a fatal error.

       Examples:

       alias_maps = hash:/etc/aliases, nis:mail.aliases
       alias_maps = hash:/etc/aliases

allow_mail_to_commands (default: alias, forward)
       Restrict local(8) mail delivery to external commands.  The default is to disallow delivery
       to "|command" in :include:  files (see aliases(5) for the text that defines this terminol-
       ogy).

       Specify zero or more of: alias,	forward  or  include,  in  order  to  allow  commands  in
       aliases(5), .forward files or in :include:  files, respectively.

       Example:

       allow_mail_to_commands = alias,forward,include

allow_mail_to_files (default: alias, forward)
       Restrict local(8) mail delivery to external files. The default is to disallow "/file/name"
       destinations in :include:  files (see aliases(5) for the text that defines this	terminol-
       ogy).

       Specify	zero or more of: alias, forward or include, in order to allow "/file/name" desti-
       nations in aliases(5), .forward files and in :include:  files, respectively.

       Example:

       allow_mail_to_files = alias,forward,include

allow_min_user (default: no)
       Allow a sender or recipient address to have `-' as the first character.	By default,  this
       is  not allowed, to avoid accidents with software that passes email addresses via the com-
       mand line. Such software would not be able to distinguish a malicious address from a  bona
       fide command-line option. Although this can be prevented by inserting a "--" option termi-
       nator into the command line, this is difficult to enforce consistently and globally.

       As of Postfix version 2.5, this feature is implemented by trivial-rewrite(8).   With  ear-
       lier  versions  this  feature  was  implemented	by  qmgr(8)  and was limited to recipient
       addresses only.

allow_percent_hack (default: yes)
       Enable the rewriting of the form "user%domain"  to  "user@domain".   This  is  enabled  by
       default.

       Note:  with Postfix version 2.2, message header address rewriting happens only when one of
       the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received  from  a	network  client  that  matches	$local_header_re-
	      write_clients,

       o      The  message  is	received  from	the network, and the remote_header_rewrite_domain
	      parameter specifies a non-empty value.

       To get the behavior before Postfix version 2.2,	specify  "local_header_rewrite_clients	=
       static:all".

       Example:

       allow_percent_hack = no

allow_untrusted_routing (default: no)
       Forward	mail  with  sender-specified  routing  (user[@%!]remote[@%!]site)  from untrusted
       clients to destinations matching $relay_domains.

       By default, this feature is turned off.	This closes a nasty open relay loophole  where	a
       backup  MX  host  can be tricked into forwarding junk mail to a primary MX host which then
       spams it out to the world.

       This parameter also controls if non-local  addresses  with  sender-specified  routing  can
       match  Postfix  access  tables.	By  default,  such  addresses cannot match Postfix access
       tables, because the address is ambiguous.

alternate_config_directories (default: empty)
       A list of non-default Postfix configuration directories that may  be  specified	with  "-c
       config_directory" on the command line, or via the MAIL_CONFIG environment parameter.

       This list must be specified in the default Postfix configuration directory, and is used by
       set-gid Postfix commands such as postqueue(1) and postdrop(1).

always_add_missing_headers (default: no)
       Always add (Resent-) From:, To:, Date: or Message-ID: headers when not  present.   Postfix
       2.6  and  later add these headers only when clients match the local_header_rewrite_clients
       parameter setting.  Earlier Postfix versions always add these headers; this may break DKIM
       signatures that cover non-existent headers.

always_bcc (default: empty)
       Optional  address  that receives a "blind carbon copy" of each message that is received by
       the Postfix mail system.

       Note: if mail to the BCC address bounces it will be returned to the sender.

       Note: automatic BCC recipients are produced only for new mail.	To  avoid  mailer  loops,
       automatic  BCC  recipients  are	not  generated after Postfix forwards mail internally, or
       after Postfix generates mail itself.

anvil_rate_time_unit (default: 60s)
       The time unit over which client connection rates and other rates are calculated.

       This feature is implemented by the anvil(8) service which is available in Postfix  version
       2.2 and later.

       The  default  interval  is relatively short. Because of the high frequency of updates, the
       anvil(8) server uses volatile memory only. Thus, information is lost whenever the  process
       terminates.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

anvil_status_update_time (default: 600s)
       How frequently the anvil(8) connection and rate limiting server logs peak  usage  informa-
       tion.

       This feature is available in Postfix 2.2 and later.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

append_at_myorigin (default: yes)
       With locally submitted mail, append the string  "@$myorigin"  to  mail  addresses  without
       domain  information.  With remotely submitted mail, append the string "@$remote_header_re-
       write_domain" instead.

       Note 1: this feature is enabled by default and must not be turned off.  Postfix	does  not
       support domain-less addresses.

       Note  2:  with Postfix version 2.2, message header address rewriting happens only when one
       of the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received  from  a	network  client  that  matches	$local_header_re-
	      write_clients,

       o      The  message  is	received  from	the network, and the remote_header_rewrite_domain
	      parameter specifies a non-empty value.

       To get the behavior before Postfix version 2.2,	specify  "local_header_rewrite_clients	=
       static:all".

append_dot_mydomain (default: yes)
       With  locally  submitted  mail,	append	the string ".$mydomain" to addresses that have no
       ".domain"   information.   With	 remotely   submitted	 mail,	  append    the    string
       ".$remote_header_rewrite_domain" instead.

       Note  1:  this  feature is enabled by default. If disabled, users will not be able to send
       mail to "user@partialdomainname" but will have to specify full domain names instead.

       Note 2: with Postfix version 2.2, message header address rewriting happens only	when  one
       of the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The  message  is	received  from	a  network  client that matches $local_header_re-
	      write_clients,

       o      The message is received from  the  network,  and	the  remote_header_rewrite_domain
	      parameter specifies a non-empty value.

       To  get	the  behavior before Postfix version 2.2, specify "local_header_rewrite_clients =
       static:all".

application_event_drain_time (default: 100s)
       How long the postkick(1) command waits for a request to enter the  server's  input  buffer
       before giving up.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1 and later.

authorized_flush_users (default: static:anyone)
       List of users who are authorized to flush the queue.

       By default, all users are allowed to flush the queue.  Access is  always  granted  if  the
       invoking  user  is the super-user or the $mail_owner user.  Otherwise, the real UID of the
       process is looked up in the system password file, and access is granted only if the corre-
       sponding  login	name is on the access list.  The username "unknown" is used for processes
       whose real UID is not found in the password file.

       Specify a list of user names, "/file/name" or "type:table" patterns, separated  by  commas
       and/or  whitespace.  The  list is matched left to right, and the search stops on the first
       match. A "/file/name" pattern is replaced by its contents; a "type:table" lookup table  is
       matched	when  a  name matches a lookup key (the lookup result is ignored).  Continue long
       lines by starting the next line with whitespace. Specify "!pattern" to exclude a name from
       the list. The form "!/file/name" is supported only in Postfix version 2.4 and later.

       This feature is available in Postfix 2.2 and later.

authorized_mailq_users (default: static:anyone)
       List of users who are authorized to view the queue.

       By  default,  all  users  are  allowed to view the queue.  Access is always granted if the
       invoking user is the super-user or the $mail_owner user.  Otherwise, the real UID  of  the
       process is looked up in the system password file, and access is granted only if the corre-
       sponding login name is on the access list.  The username "unknown" is used  for	processes
       whose real UID is not found in the password file.

       Specify	a  list of user names, "/file/name" or "type:table" patterns, separated by commas
       and/or whitespace. The list is matched left to right, and the search stops  on  the  first
       match.  A "/file/name" pattern is replaced by its contents; a "type:table" lookup table is
       matched when a name matches a lookup key (the lookup result is  ignored).   Continue  long
       lines by starting the next line with whitespace. Specify "!pattern" to exclude a user name
       from the list. The form "!/file/name" is supported only in Postfix version 2.4 and later.

       This feature is available in Postfix 2.2 and later.

authorized_submit_users (default: static:anyone)
       List of users who are authorized to submit mail with the sendmail(1) command (and with the
       privileged postdrop(1) helper command).

       By  default, all users are allowed to submit mail.  Otherwise, the real UID of the process
       is looked up in the system password file, and access is granted only if the  corresponding
       login name is on the access list.  The username "unknown" is used for processes whose real
       UID is not found in the password file. To deny mail submission access to all users specify
       an empty list.

       Specify	a  list of user names, "/file/name" or "type:table" patterns, separated by commas
       and/or whitespace. The list is matched left to right, and the search stops  on  the  first
       match.  A "/file/name" pattern is replaced by its contents; a "type:table" lookup table is
       matched when a name matches a lookup key (the lookup result is  ignored).   Continue  long
       lines by starting the next line with whitespace. Specify "!pattern" to exclude a user name
       from the list. The form "!/file/name" is supported only in Postfix version 2.4 and later.

       Example:

       authorized_submit_users = !www, static:all

       This feature is available in Postfix 2.2 and later.

authorized_verp_clients (default: $mynetworks)
       What SMTP clients are allowed to specify the XVERP command.  This  command  requests  that
       mail be delivered one recipient at a time with a per recipient return address.

       By default, only trusted clients are allowed to specify XVERP.

       This  parameter was introduced with Postfix version 1.1.  Postfix version 2.1 renamed this
       parameter to smtpd_authorized_verp_clients and changed the default to none.

       Specify a list of network/netmask patterns, separated by  commas  and/or  whitespace.  The
       mask  specifies	the  number  of  bits in the network part of a host address. You can also
       specify hostnames or .domain names (the initial dot causes the domain to  match	any  name
       below  it),  "/file/name" or "type:table" patterns.  A "/file/name" pattern is replaced by
       its contents; a "type:table" lookup table is matched when a table entry matches	a  lookup
       string (the lookup result is ignored).  Continue long lines by starting the next line with
       whitespace. Specify "!pattern" to exclude an address or network block from the  list.  The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version  6  address  information  must  be  specified  inside  [] in the autho-
       rized_verp_clients value,  and  in  files  specified  with  "/file/name".   IP  version	6
       addresses  contain  the ":" character, and would otherwise be confused with a "type:table"
       pattern.

backwards_bounce_logfile_compatibility (default: yes)
       Produce additional bounce(8) logfile records that can be read by Postfix  versions  before
       2.0. The current and more extensible "name = value" format is needed in order to implement
       more sophisticated functionality.

       This feature is available in Postfix 2.1 and later.

berkeley_db_create_buffer_size (default: 16777216)
       The per-table I/O buffer size for programs that create Berkeley DB hash or  btree  tables.
       Specify a byte count.

       This feature is available in Postfix 2.0 and later.

berkeley_db_read_buffer_size (default: 131072)
       The  per-table  I/O  buffer  size for programs that read Berkeley DB hash or btree tables.
       Specify a byte count.

       This feature is available in Postfix 2.0 and later.

best_mx_transport (default: empty)
       Where the Postfix SMTP client should deliver mail when it detects a "mail  loops  back  to
       myself"	error  condition. This happens when the local MTA is the best SMTP mail exchanger
       for a destination not listed in $mydestination, $inet_interfaces, $proxy_interfaces, $vir-
       tual_alias_domains,  or	$virtual_mailbox_domains.   By	default,  the Postfix SMTP client
       returns such mail as undeliverable.

       Specify, for example, "best_mx_transport = local" to pass the mail from the  Postfix  SMTP
       client to the local(8) delivery agent. You can specify any message delivery "transport" or
       "transport:nexthop" that is defined in the master.cf file.  See	the  transport(5)  manual
       page for the syntax and meaning of "transport" or "transport:nexthop".

       However,  this feature is expensive because it ties up a Postfix SMTP client process while
       the local(8) delivery agent is doing its work. It is more efficient (for Postfix) to  list
       all hosted domains in a table or database.

biff (default: yes)
       Whether or not to use the local biff service.  This service sends "new mail" notifications
       to users who have requested new mail notification with the UNIX command "biff y".

       For compatibility reasons this feature is on by default.  On systems with lots of interac-
       tive  users,  the biff service can be a performance drain.  Specify "biff = no" in main.cf
       to disable.

body_checks (default: empty)
       Optional lookup tables for content inspection as specified in  the  body_checks(5)  manual
       page.

       Note:  with Postfix versions before 2.0, these rules inspect all content after the primary
       message headers.

body_checks_size_limit (default: 51200)
       How much text in a message body segment (or attachment, if you prefer to use that term) is
       subjected to body_checks inspection.  The amount of text is limited to avoid scanning huge
       attachments.

       This feature is available in Postfix 2.0 and later.

bounce_notice_recipient (default: postmaster)
       The recipient of postmaster notifications with the message headers of  mail  that  Postfix
       did not deliver and of SMTP conversation transcripts of mail that Postfix did not receive.
       This feature is enabled with the notify_classes parameter.

bounce_queue_lifetime (default: 5d)
       The maximal time a bounce message is queued before it  is  considered  undeliverable.   By
       default, this is the same as the queue life time for regular mail.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is d (days).

       Specify 0 when mail delivery should be tried only once.

       This feature is available in Postfix 2.1 and later.

bounce_service_name (default: bounce)
       The name of the bounce(8) service. This service maintains  a  record  of  failed  delivery
       attempts and generates non-delivery notifications.

       This feature is available in Postfix 2.0 and later.

bounce_size_limit (default: 50000)
       The  maximal  amount of original message text that is sent in a non-delivery notification.
       Specify a byte count.  A message is returned as either message/rfc822 (the complete origi-
       nal)  or as text/rfc822-headers (the headers only).  With Postfix version 2.4 and earlier,
       a message is always returned as message/rfc822 and is truncated when it exceeds	the  size
       limit.

       Notes:

       o      If  you  increase this limit, then you should increase the mime_nesting_limit value
	      proportionally.

       o      Be careful when making changes.  Excessively large values will result in	the  loss
	      of non-delivery notifications, when a bounce message size exceeds a local or remote
	      MTA's message size limit.

bounce_template_file (default: empty)
       Pathname of a configuration file with bounce message templates.	These override the built-
       in  templates  of  delivery status notification (DSN) messages for undeliverable mail, for
       delayed mail, successful delivery, or delivery verification.  The  bounce(5)  manual  page
       describes how to edit and test template files.

       Template  message  body text may contain $name references to Postfix configuration parame-
       ters. The result of $name expansion can be previewed with "postconf -b  file_name"  before
       the file is placed into the Postfix configuration directory.

       This feature is available in Postfix 2.3 and later.

broken_sasl_auth_clients (default: no)
       Enable  inter-operability with SMTP clients that implement an obsolete version of the AUTH
       command (RFC 4954). Examples of such clients are MicroSoft Outlook Express version  4  and
       MicroSoft Exchange version 5.0.

       Specify	"broken_sasl_auth_clients = yes" to have Postfix advertise AUTH support in a non-
       standard way.

canonical_classes (default: envelope_sender, envelope_recipient, header_sender, header_recipient)

       What  addresses are subject to canonical_maps address mapping.  By default, canonical_maps
       address mapping is applied to envelope sender  and  recipient  addresses,  and  to  header
       sender and header recipient addresses.

       Specify one or more of: envelope_sender, envelope_recipient, header_sender, header_recipi-
       ent

       This feature is available in Postfix 2.2 and later.

canonical_maps (default: empty)
       Optional address mapping lookup tables for message headers and envelopes. The  mapping  is
       applied	to both sender and recipient addresses, in both envelopes and in headers, as con-
       trolled with the canonical_classes parameter. This is typically used  to  clean	up  dirty
       addresses  from legacy mail systems, or to replace login names by Firstname.Lastname.  The
       table format and lookups are documented	in  canonical(5).  For	an  overview  of  Postfix
       address manipulations see the ADDRESS_REWRITING_README document.

       If  you	use this feature, run "postmap /etc/postfix/canonical" to build the necessary DBM
       or DB file after every change. The changes will become visible after a minute or so.   Use
       "postfix reload" to eliminate the delay.

       Note:  with  Postfix version 2.2, message header address mapping happens only when message
       header address rewriting is enabled:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received  from  a	network  client  that  matches	$local_header_re-
	      write_clients,

       o      The  message  is	received  from	the network, and the remote_header_rewrite_domain
	      parameter specifies a non-empty value.

       To get the behavior before Postfix version 2.2,	specify  "local_header_rewrite_clients	=
       static:all".

       Examples:

       canonical_maps = dbm:/etc/postfix/canonical
       canonical_maps = hash:/etc/postfix/canonical

cleanup_service_name (default: cleanup)
       The  name  of  the  cleanup(8)  service. This service rewrites addresses into the standard
       form, and performs canonical(5) address mapping and virtual(5) aliasing.

       This feature is available in Postfix 2.0 and later.

command_directory (default: see postconf -d output)
       The location of all postfix administrative commands.

command_execution_directory (default: empty)
       The local(8) delivery agent working directory for delivery to external  command.   Failure
       to change directory causes the delivery to be deferred.

       The  following  $name expansions are done on command_execution_directory before the direc-
       tory is changed. Expansion happens in the context of the delivery request.  The result  of
       $name  expansion  is  filtered  with  the  character set that is specified with the execu-
       tion_directory_expansion_filter parameter.

       $user  The recipient's username.

       $shell The recipient's login shell pathname.

       $home  The recipient's home directory.

       $recipient
	      The full recipient address.

       $extension
	      The optional recipient address extension.

       $domain
	      The recipient domain.

       $local The entire recipient localpart.

       $recipient_delimiter
	      The system-wide recipient address extension delimiter.

       ${name?value}
	      Expands to value when $name is non-empty.

       ${name:value}
	      Expands to value when $name is empty.

       Instead of $name you can also specify ${name} or $(name).

       This feature is available in Postfix 2.2 and later.

command_expansion_filter (default: see postconf -d output)
       Restrict the characters that the local(8) delivery agent allows	in  $name  expansions  of
       $mailbox_command and $command_execution_directory.  Characters outside the allowed set are
       replaced by underscores.

command_time_limit (default: 1000s)
       Time limit for delivery to external commands. This limit is used by the local(8)  delivery
       agent, and is the default time limit for delivery by the pipe(8) delivery agent.

       Note:  if  you set this time limit to a large value you must update the global ipc_timeout
       parameter as well.

config_directory (default: see postconf -d output)
       The default location of the Postfix main.cf and master.cf configuration files. This can be
       overruled via the following mechanisms:

       o      The MAIL_CONFIG environment variable (daemon processes and commands).

       o      The "-c" command-line option (commands only).

       With  Postfix  command  that  run  with	set-gid  privileges,  a config_directory override
       requires either root privileges, or it requires that the  directory  is	listed	with  the
       alternate_config_directories parameter in the default main.cf file.

connection_cache_protocol_timeout (default: 5s)
       Time  limit  for  connection cache connect, send or receive operations.	The time limit is
       enforced in the client.

       This feature is available in Postfix 2.3 and later.

connection_cache_service_name (default: scache)
       The name of the scache(8) connection cache service.  This service maintains a limited pool
       of cached sessions.

       This feature is available in Postfix 2.2 and later.

connection_cache_status_update_time (default: 600s)
       How  frequently	the  scache(8) server logs usage statistics with connection cache hit and
       miss rates for logical destinations and for physical endpoints.

connection_cache_ttl_limit (default: 2s)
       The maximal time-to-live value that the scache(8) connection cache server allows. Requests
       that specify a larger TTL will be stored with the maximum allowed TTL. The purpose of this
       additional control is to protect the infrastructure against careless people. The cache TTL
       is already bounded by $max_idle.

content_filter (default: empty)
       After  the  message is queued, send the entire message to the specified transport:destina-
       tion. The transport name specifies the first field of a mail delivery agent definition  in
       master.cf;  the	syntax of the next-hop destination is described in the manual page of the
       corresponding delivery agent.  More information about external content filters is  in  the
       Postfix FILTER_README file.

       Notes:

       o      This  setting  has  lower  precedence  than a FILTER action that is specified in an
	      access(5), header_checks(5) or body_checks(5) table.

       o      The meaning of an empty next-hop filter destination is version dependent.   Postfix
	      2.7 and later will use the recipient domain; earlier versions will use $myhostname.
	      Specify "default_filter_nexthop = $myhostname" for compatibility with  Postfix  2.6
	      or  earlier,  or	specify a content_filter value with an explicit next-hop destina-
	      tion.

cyrus_sasl_config_path (default: empty)
       Search path for Cyrus SASL application configuration files, currently used only to  locate
       the  $smtpd_sasl_path.conf  file.   Specify  zero or more directories separated by a colon
       character, or an empty value to use Cyrus SASL's built-in search path.

       This feature is available in Postfix 2.5 and later when compiled with Cyrus SASL 2.1.22 or
       later.

daemon_directory (default: see postconf -d output)
       The  directory  with  Postfix  support  programs and daemon programs.  These should not be
       invoked directly by humans. The directory must be owned by root.

daemon_timeout (default: 18000s)
       How much time a Postfix daemon process may take to handle a request before  it  is  termi-
       nated by a built-in watchdog timer.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

data_directory (default: see postconf -d output)
       The directory with Postfix-writable data files (for example:  caches,  pseudo-random  num-
       bers).	This  directory  must  be owned by the mail_owner account, and must not be shared
       with non-Postfix software.

       This feature is available in Postfix 2.5 and later.

debug_peer_level (default: 2)
       The increment in verbose logging level when a remote client or server matches a pattern in
       the debug_peer_list parameter.

debug_peer_list (default: empty)
       Optional  list  of remote client or server hostname or network address patterns that cause
       the verbose logging level to increase by the amount specified in $debug_peer_level.

       Specify domain names, network/netmask  patterns,  "/file/name"  patterns  or  "type:table"
       lookup tables. The right-hand side result from "type:table" lookups is ignored.

       Pattern	matching  of  domain  names is controlled by the parent_domain_matches_subdomains
       parameter.

       Examples:

       debug_peer_list = 127.0.0.1
       debug_peer_list = example.com

debugger_command (default: empty)
       The external command to execute when a Postfix daemon  program  is  invoked  with  the  -D
       option.

       Use  "command .. & sleep 5" so that the debugger can attach before the process marches on.
       If you use an X-based debugger, be sure to set up  your	XAUTHORITY  environment  variable
       before starting Postfix.

       Example:

       debugger_command =
	   PATH=/usr/bin:/usr/X11R6/bin
	   ddd $daemon_directory/$process_name $process_id & sleep 5

default_database_type (default: see postconf -d output)
       The  default database type for use in newaliases(1), postalias(1) and postmap(1) commands.
       On many UNIX systems the default type is either dbm or hash. The default setting is frozen
       when the Postfix system is built.

       Examples:

       default_database_type = hash
       default_database_type = dbm

default_delivery_slot_cost (default: 5)
       How often the Postfix queue manager's scheduler is allowed to preempt delivery of one mes-
       sage with another.

       Each transport maintains a so-called "available delivery slot counter" for  each  message.
       One  message can be preempted by another one when the other message can be delivered using
       no more delivery slots (i.e., invocations of delivery agents)  than  the  current  message
       counter has accumulated (or will eventually accumulate - see about slot loans below). This
       parameter controls  how	often  is  the	counter  incremented  -  it  happens  after  each
       default_delivery_slot_cost recipients have been delivered.

       The  cost of 0 is used to disable the preempting scheduling completely.	The minimum value
       the scheduling algorithm can use is 2 - use  it	if  you  want  to  maximize  the  message
       throughput  rate.  Although  there is no maximum, it doesn't make much sense to use values
       above say 50.

       The only reason why the value of 2 is not the default is the way  this  parameter  affects
       the  delivery  of  mailing-list mail. In the worst case, their delivery can take somewhere
       between (cost+1/cost) and (cost/cost-1) times more than if the  preemptive  scheduler  was
       disabled.  The  default	value of 5 turns out to provide reasonable message response times
       while making sure the mailing-list deliveries are not extended by more than 20-25  percent
       even in the worst case.

       Use transport_delivery_slot_cost to specify a transport-specific override, where transport
       is the master.cf name of the message delivery transport.

       Examples:

       default_delivery_slot_cost = 0
       default_delivery_slot_cost = 2

default_delivery_slot_discount (default: 50)
       The default value for transport-specific _delivery_slot_discount settings.

       This parameter speeds up the moment when a message preemption can happen. Instead of wait-
       ing until the full amount of delivery slots required is available, the preemption can hap-
       pen when transport_delivery_slot_discount percent  of  the  required  amount  plus  trans-
       port_delivery_slot_loan	still  remains to be accumulated.  Note that the full amount will
       still have to be accumulated before another preemption can take place later.

       Use transport_delivery_slot_discount  to  specify  a  transport-specific  override,  where
       transport is the master.cf name of the message delivery transport.

default_delivery_slot_loan (default: 3)
       The default value for transport-specific _delivery_slot_loan settings.

       This parameter speeds up the moment when a message preemption can happen. Instead of wait-
       ing until the full amount of delivery slots required is available, the preemption can hap-
       pen  when  transport_delivery_slot_discount  percent  of  the  required amount plus trans-
       port_delivery_slot_loan still remains to be accumulated.  Note that the full  amount  will
       still have to be accumulated before another preemption can take place later.

       Use transport_delivery_slot_loan to specify a transport-specific override, where transport
       is the master.cf name of the message delivery transport.

default_destination_concurrency_failed_cohort_limit (default: 1)
       How many pseudo-cohorts must suffer connection or handshake failure before a specific des-
       tination  is  considered  unavailable (and further delivery is suspended). Specify zero to
       disable this feature. A destination's pseudo-cohort failure count is  reset  each  time	a
       delivery completes without connection or handshake failure for that specific destination.

       A pseudo-cohort is the number of deliveries equal to a destination's delivery concurrency.

       Use  transport_destination_concurrency_failed_cohort_limit to specify a transport-specific
       override, where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5. The default setting is compatible  with  earlier
       Postfix versions.

default_destination_concurrency_limit (default: 20)
       The  default  maximal  number of parallel deliveries to the same destination.  This is the
       default limit for delivery via the  lmtp(8),  pipe(8),  smtp(8)	and  virtual(8)  delivery
       agents.	With per-destination recipient limit > 1, a destination is a domain, otherwise it
       is a recipient.

       Use transport_destination_concurrency_limit  to	specify  a  transport-specific	override,
       where transport is the master.cf name of the message delivery transport.

default_destination_concurrency_negative_feedback (default: 1)
       The  per-destination  amount  of  delivery concurrency negative feedback, after a delivery
       completes with a connection or handshake failure. Feedback values are in  the  range  0..1
       inclusive.  With  negative  feedback,  concurrency  is  decremented  at the beginning of a
       sequence of length 1/feedback. This is unlike  positive	feedback,  where  concurrency  is
       incremented at the end of a sequence of length 1/feedback.

       As  of  Postfix version 2.5, negative feedback cannot reduce delivery concurrency to zero.
       Instead, a destination is marked  dead  (further  delivery  suspended)  after  the  failed
       pseudo-cohort   count   reaches	$default_destination_concurrency_failed_cohort_limit  (or
       $transport_destination_concurrency_failed_cohort_limit).  To make the scheduler completely
       immune  to  connection  or  handshake  failures,  specify a zero feedback value and a zero
       failed pseudo-cohort limit.

       Specify one of the following forms:

       number

       number / number
	      Constant feedback. The value must be in the range 0..1 inclusive.  The default set-
	      ting  of	"1" is compatible with Postfix versions before 2.5, where a destination's
	      delivery concurrency is throttled down to zero  (and  further  delivery  suspended)
	      after a single failed pseudo-cohort.

       number / concurrency
	      Variable	feedback of "number / (delivery concurrency)".	The number must be in the
	      range 0..1 inclusive. With number equal to "1", a  destination's	delivery  concur-
	      rency is decremented by 1 after each failed pseudo-cohort.

       A pseudo-cohort is the number of deliveries equal to a destination's delivery concurrency.

       Use  transport_destination_concurrency_negative_feedback  to  specify a transport-specific
       override, where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5. The default setting is compatible  with  earlier
       Postfix versions.

default_destination_concurrency_positive_feedback (default: 1)
       The  per-destination  amount  of  delivery concurrency positive feedback, after a delivery
       completes without connection or handshake failure. Feedback values are in the  range  0..1
       inclusive.  The concurrency increases until it reaches the per-destination maximal concur-
       rency limit. With positive feedback, concurrency is incremented at the end of  a  sequence
       with length 1/feedback. This is unlike negative feedback, where concurrency is decremented
       at the start of a sequence of length 1/feedback.

       Specify one of the following forms:

       number

       number / number
	      Constant feedback.  The value must be in the range 0..1 inclusive. The default set-
	      ting  of	"1" is compatible with Postfix versions before 2.5, where a destination's
	      delivery concurrency doubles after each successful pseudo-cohort.

       number / concurrency
	      Variable feedback of "number / (delivery concurrency)".  The number must be in  the
	      range  0..1  inclusive.  With number equal to "1", a destination's delivery concur-
	      rency is incremented by 1 after each successful pseudo-cohort.

       A pseudo-cohort is the number of deliveries equal to a destination's delivery concurrency.

       Use transport_destination_concurrency_positive_feedback to  specify  a  transport-specific
       override, where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5 and later.

default_destination_rate_delay (default: 0s)
       The  default  amount  of  delay that is inserted between individual deliveries to the same
       destination; with per-destination recipient limit > 1, a destination is a  domain,  other-
       wise it is a recipient.

       To  enable  the	delay,	specify a non-zero time value (an integral value plus an optional
       one-letter suffix that specifies the time unit).

       Time units: s (seconds), m (minutes), h (hours), d (days), w  (weeks).  The  default  time
       unit is s (seconds).

       NOTE:  the  delay is enforced by the queue manager. The delay timer state does not survive
       "postfix reload" or "postfix stop".

       Use transport_destination_rate_delay  to  specify  a  transport-specific  override,  where
       transport is the master.cf name of the message delivery transport.

       NOTE:  with  a  non-zero  _destination_rate_delay, specify a transport_destination_concur-
       rency_failed_cohort_limit of 10 or more to prevent Postfix from deferring all mail for the
       same destination after only one connection or handshake error.

       This feature is available in Postfix 2.5 and later.

default_destination_recipient_limit (default: 50)
       The  default maximal number of recipients per message delivery.	This is the default limit
       for delivery via the lmtp(8), pipe(8), smtp(8) and virtual(8) delivery agents.

       Setting this parameter to a value of 1 changes the meaning of the corresponding per-desti-
       nation concurrency limit from concurrency per domain into concurrency per recipient.

       Use  transport_destination_recipient_limit to specify a transport-specific override, where
       transport is the master.cf name of the message delivery transport.

default_extra_recipient_limit (default: 1000)
       The default value for the extra per-transport limit imposed on  the  number  of	in-memory
       recipients.   This  extra recipient space is reserved for the cases when the Postfix queue
       manager's scheduler preempts one message with another and suddenly needs some extra recip-
       ients slots for the chosen message in order to avoid performance degradation.

       Use transport_extra_recipient_limit to specify a transport-specific override, where trans-
       port is the master.cf name of the message delivery transport.

default_filter_nexthop (default: empty)
       When a content_filter or FILTER request specifies no explicit  next-hop	destination,  use
       $default_filter_nexthop instead; when that value is empty, use the domain in the recipient
       address.  Specify "default_filter_nexthop = $myhostname" for  compatibility  with  Postfix
       version	2.6  and  earlier,  or	specify  an  explicit next-hop destination with each con-
       tent_filter value or FILTER action.

       This feature is available in Postfix 2.7 and later.

default_minimum_delivery_slots (default: 3)
       How many recipients a message must have in order to invoke  the	Postfix  queue	manager's
       scheduling  algorithm  at  all.	 Messages which would never accumulate at least this many
       delivery slots (subject to slot cost parameter as well) are never preempted.

       Use transport_minimum_delivery_slots  to  specify  a  transport-specific  override,  where
       transport is the master.cf name of the message delivery transport.

default_privs (default: nobody)
       The  default  rights  used by the local(8) delivery agent for delivery to external file or
       command.  These rights are used when delivery is requested from an aliases(5) file that is
       owned  by  root,  or  when delivery is done on behalf of root. DO NOT SPECIFY A PRIVILEGED
       USER OR THE POSTFIX OWNER.

default_process_limit (default: 100)
       The default maximal number of Postfix child processes that provide a given  service.  This
       limit can be overruled for specific services in the master.cf file.

default_rbl_reply (default: see postconf -d output)
       The  default  SMTP server response template for a request that is rejected by an RBL-based
       restriction.  This  template  can  be  overruled  by  specific  entries	in  the  optional
       rbl_reply_maps lookup table.

       This feature is available in Postfix 2.0 and later.

       The template is subject to exactly one level of $name substitution:

       $client
	      The client hostname and IP address, formatted as name[address].

       $client_address
	      The client IP address.

       $client_name
	      The  client  hostname  or  "unknown".  See  reject_unknown_client_hostname for more
	      details.

       $reverse_client_name
	      The   client   hostname	from   address->name   lookup,	 or    "unknown".     See
	      reject_unknown_reverse_client_hostname for more details.

       $helo_name
	      The hostname given in HELO or EHLO command or empty string.

       $rbl_class
	      The  blacklisted entity type: Client host, Helo command, Sender address, or Recipi-
	      ent address.

       $rbl_code
	      The numerical SMTP response code, as specified with the  maps_rbl_reject_code  con-
	      figuration  parameter. Note: The numerical SMTP response code is required, and must
	      appear at the start of the reply. With Postfix version 2.3 and later this  informa-
	      tion may be followed by an RFC 3463 enhanced status code.

       $rbl_domain
	      The RBL domain where $rbl_what is blacklisted.

       $rbl_reason
	      The reason why $rbl_what is blacklisted, or an empty string.

       $rbl_what
	      The  entity  that  is  blacklisted (an IP address, a hostname, a domain name, or an
	      email address whose domain was blacklisted).

       $recipient
	      The recipient address or <> in case of the null address.

       $recipient_domain
	      The recipient domain or empty string.

       $recipient_name
	      The recipient address localpart or <> in case of null address.

       $sender
	      The sender address or <> in case of the null address.

       $sender_domain
	      The sender domain or empty string.

       $sender_name
	      The sender address localpart or <> in case of the null address.

       ${name?text}
	      Expands to `text' if $name is not empty.

       ${name:text}
	      Expands to `text' if $name is empty.

       Instead of $name you can also specify ${name} or $(name).

       Note: when an enhanced status code is specified in an RBL reply template, it is subject to
       modification.   The  following transformations are needed when the same RBL reply template
       is used for client, helo, sender, or recipient access restrictions.

       o      When rejecting a sender address, the Postfix SMTP server will transform a recipient
	      DSN  status  (e.g., 4.1.1-4.1.6) into the corresponding sender DSN status, and vice
	      versa.

       o      When rejecting non-address information (such as the HELO command	argument  or  the
	      client hostname/address), the Postfix SMTP server will transform a sender or recip-
	      ient DSN status into a generic non-address DSN status (e.g., 4.0.0).

default_recipient_limit (default: 20000)
       The default per-transport upper limit on the number of in-memory recipients.  These limits
       take  priority  over  the  global  qmgr_message_recipient_limit after the message has been
       assigned  to  the  respective  transports.   See  also  default_extra_recipient_limit  and
       qmgr_message_recipient_minimum.

       Use transport_recipient_limit to specify a transport-specific override, where transport is
       the master.cf name of the message delivery transport.

default_recipient_refill_delay (default: 5s)
       The default per-transport maximum delay between recipients refills.  When not all  message
       recipients fit into the memory at once, keep loading more of them at least once every this
       many seconds.  This is used to make sure the recipients are refilled in timely manner even
       when $default_recipient_refill_limit is too high for too slow deliveries.

       Use  transport_recipient_refill_delay  to  specify  a  transport-specific  override, where
       transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.4 and later.

default_recipient_refill_limit (default: 100)
       The default per-transport limit on the number of recipients refilled at	once.	When  not
       all  message  recipients fit into the memory at once, keep loading more of them in batches
       of at least this many at a time.   See  also  $default_recipient_refill_delay,  which  may
       result  in  recipient  batches  lower  than  this when this limit is too high for too slow
       deliveries.

       Use transport_recipient_refill_limit  to  specify  a  transport-specific  override,  where
       transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.4 and later.

default_transport (default: smtp)
       The  default mail delivery transport and next-hop destination for destinations that do not
       match $mydestination, $inet_interfaces, $proxy_interfaces,  $virtual_alias_domains,  $vir-
       tual_mailbox_domains,  or  $relay_domains.   This  information  can  be overruled with the
       sender_dependent_default_transport_maps parameter and with the transport(5) table.

       In order of decreasing precedence, the nexthop destination is  taken  from  $sender_depen-
       dent_default_transport_maps, $default_transport, $sender_dependent_relayhost_maps, $relay-
       host, or from the recipient domain.

       Specify a string of the form transport:nexthop, where transport is  the	name  of  a  mail
       delivery transport defined in master.cf.  The :nexthop destination is optional; its syntax
       is documented in the manual page of the corresponding delivery agent.

       Example:

       default_transport = uucp:relayhostname

default_verp_delimiters (default: +=)
       The two default VERP delimiter characters. These are used when no explicit delimiters  are
       specified with the SMTP XVERP command or with the "sendmail -V" command-line option. Spec-
       ify characters that are allowed by the verp_delimiter_filter setting.

       This feature is available in Postfix 1.1 and later.

defer_code (default: 450)
       The numerical Postfix SMTP server response code when  a	remote	SMTP  client  request  is
       rejected by the "defer" restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

defer_service_name (default: defer)
       The  name  of  the  defer service. This service is implemented by the bounce(8) daemon and
       maintains a record of failed delivery attempts and generates non-delivery notifications.

       This feature is available in Postfix 2.0 and later.

defer_transports (default: empty)
       The names of message delivery transports that  should  not  deliver  mail  unless  someone
       issues "sendmail -q" or equivalent. Specify zero or more names of mail delivery transports
       names that appear in the first field of master.cf.

       Example:

       defer_transports = smtp

delay_logging_resolution_limit (default: 2)
       The maximal number of digits after the decimal point when logging sub-second delay values.
       Specify a number in the range 0..6.

       Large  delay  values are rounded off to an integral number seconds; delay values below the
       delay_logging_resolution_limit are logged as "0", and small delay values are  logged  with
       at most two-digit precision.

       The format of the "delays=a/b/c/d" logging is as follows:

       o      a = time from message arrival to last active queue entry

       o      b = time from last active queue entry to connection setup

       o      c = time in connection setup, including DNS, EHLO and STARTTLS

       o      d = time in message transmission

       This feature is available in Postfix 2.3 and later.

delay_notice_recipient (default: postmaster)
       The  recipient of postmaster notifications with the message headers of mail that cannot be
       delivered within $delay_warning_time time units.

       This feature is enabled with the delay_warning_time parameter.

delay_warning_time (default: 0h)
       The time after which the sender receives the message headers of mail that is still queued.

       To enable this feature, specify a non-zero time value (an integral value plus an  optional
       one-letter suffix that specifies the time unit).

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is h (hours).

deliver_lock_attempts (default: 20)
       The maximal number of attempts to acquire an exclusive lock on a mailbox file or bounce(8)
       logfile.

deliver_lock_delay (default: 1s)
       The time between attempts to acquire an exclusive lock on a mailbox file or bounce(8) log-
       file.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

destination_concurrency_feedback_debug (default: no)
       Make the queue manager's feedback algorithm verbose for performance analysis purposes.

       This feature is available in Postfix 2.5 and later.

detect_8bit_encoding_header (default: yes)
       Automatically  detect  8BITMIME body content by looking at Content-Transfer-Encoding: mes-
       sage headers; historically, this behavior was hard-coded to be "always on".

       This feature is available in Postfix 2.5 and later.

disable_dns_lookups (default: no)
       Disable DNS lookups in the Postfix SMTP and LMTP clients. When disabled, hosts are  looked
       up with the getaddrinfo() system library routine which normally also looks in /etc/hosts.

       DNS lookups are enabled by default.

disable_mime_input_processing (default: no)
       Turn  off  MIME	processing  while receiving mail. This means that no special treatment is
       given to Content-Type: message headers, and that all text after the initial message  head-
       ers is considered to be part of the message body.

       This feature is available in Postfix 2.0 and later.

       Mime  input  processing	is  enabled  by default, and is needed in order to recognize MIME
       headers in message content.

disable_mime_output_conversion (default: no)
       Disable the conversion of 8BITMIME format to  7BIT  format.   Mime  output  conversion  is
       needed when the destination does not advertise 8BITMIME support.

       This feature is available in Postfix 2.0 and later.

disable_verp_bounces (default: no)
       Disable sending one bounce report per recipient.

       The default, one per recipient, is what ezmlm needs.

       This feature is available in Postfix 1.1 and later.

disable_vrfy_command (default: no)
       Disable the SMTP VRFY command. This stops some techniques used to harvest email addresses.

       Example:

       disable_vrfy_command = no

dnsblog_reply_delay (default: 0s)
       A debugging aid to artifically delay DNS responses.

       This feature is available in Postfix 2.8.

dnsblog_service_name (default: dnsblog)
       The  name  of  the  dnsblog(8)  service	entry  in  master.cf.  This  service performs DNS
       white/blacklist lookups.

       This feature is available in Postfix 2.8 and later.

dont_remove (default: 0)
       Don't remove queue files and save them to the "saved" mail queue.   This  is  a	debugging
       aid.   To  inspect  the	envelope information and content of a Postfix queue file, use the
       postcat(1) command.

double_bounce_sender (default: double-bounce)
       The sender address of postmaster notifications that are generated by the mail system.  All
       mail to this address is silently discarded, in order to terminate mail bounce loops.

duplicate_filter_limit (default: 1000)
       The  maximal number of addresses remembered by the address duplicate filter for aliases(5)
       or virtual(5) alias expansion, or for showq(8) queue displays.

empty_address_default_transport_maps_lookup_key (default: <>)
       The sender_dependent_default_transport_maps search string that will be used instead of the
       null sender address.

       This feature is available in Postfix 2.7 and later.

empty_address_recipient (default: MAILER-DAEMON)
       The  recipient  of  mail  addressed  to	the  null  address.  Postfix does not accept such
       addresses in SMTP commands, but they may still be created locally as the result of config-
       uration or software error.

empty_address_relayhost_maps_lookup_key (default: <>)
       The  sender_dependent_relayhost_maps  search  string that will be used instead of the null
       sender address.

       This feature is available in Postfix 2.5 and later. With earlier  versions,  sender_depen-
       dent_relayhost_maps lookups were skipped for the null sender address.

enable_errors_to (default: no)
       Report mail delivery errors to the address specified with the non-standard Errors-To: mes-
       sage header, instead of the envelope sender address (this feature is removed with  Postfix
       version	2.2,  is  turned off by default with Postfix version 2.1, and is always turned on
       with older Postfix versions).

enable_original_recipient (default: yes)
       Enable support for the X-Original-To message header. This  header  is  needed  for  multi-
       recipient mailboxes.

       When this parameter is set to yes, the cleanup(8) daemon performs duplicate elimination on
       distinct pairs of (original recipient, rewritten recipient), and generates non-empty orig-
       inal recipient queue file records.

       When  this parameter is set to no, the cleanup(8) daemon performs duplicate elimination on
       the rewritten recipient address only, and generates empty original  recipient  queue  file
       records.

       This  feature is available in Postfix 2.1 and later. With Postfix version 2.0, support for
       the X-Original-To message header is always turned on. Postfix versions before 2.0 have  no
       support for the X-Original-To message header.

error_notice_recipient (default: postmaster)
       The  recipient of postmaster notifications about mail delivery problems that are caused by
       policy, resource, software or protocol errors.  These notifications are enabled	with  the
       notify_classes parameter.

error_service_name (default: error)
       The  name of the error(8) pseudo delivery agent. This service always returns mail as unde-
       liverable.

       This feature is available in Postfix 2.0 and later.

execution_directory_expansion_filter (default: see postconf -d output)
       Restrict the characters that the local(8) delivery agent allows	in  $name  expansions  of
       $command_execution_directory.   Characters  outside the allowed set are replaced by under-
       scores.

       This feature is available in Postfix 2.2 and later.

expand_owner_alias (default: no)
       When delivering to an alias "aliasname" that has an "owner-aliasname" companion alias, set
       the  envelope  sender  address  to the expansion of the "owner-aliasname" alias. Normally,
       Postfix sets the envelope sender address to the name of the "owner-aliasname" alias.

export_environment (default: see postconf -d output)
       The list of environment variables that a Postfix process will export to	non-Postfix  pro-
       cesses. The TZ variable is needed for sane time keeping on System-V-ish systems.

       Specify	a  list  of  names and/or name=value pairs, separated by whitespace or comma. The
       name=value form is supported with Postfix version 2.1 and later.

       Example:

       export_environment = TZ PATH=/bin:/usr/bin

extract_recipient_limit (default: 10240)
       The maximal number of recipient addresses that Postfix will extract from  message  headers
       when mail is submitted with "sendmail -t".

       This feature was removed in Postfix version 2.1.

fallback_relay (default: empty)
       Optional  list  of  relay  hosts  for  SMTP  destinations  that can't be found or that are
       unreachable. With Postfix 2.3 this parameter is renamed to smtp_fallback_relay.

       By default, mail is returned to the sender when a destination is not found,  and  delivery
       is deferred when a destination is unreachable.

       The  fallback  relays  must  be	SMTP  destinations.  Specify  a  domain, host, host:port,
       [host]:port, [address] or [address]:port; the form [host] turns off MX  lookups.   If  you
       specify multiple SMTP destinations, Postfix will try them in the specified order.

       Note:  before  Postfix 2.2, do not use the fallback_relay feature when relaying mail for a
       backup or primary MX domain. Mail would loop between the Postfix MX  host  and  the  fall-
       back_relay host when the final destination is unavailable.

       o      In main.cf specify "relay_transport = relay",

       o      In  master.cf  specify  "-o fallback_relay =" (i.e., empty) at the end of the relay
	      entry.

       o      In transport maps, specify "relay:nexthop..."  as the right-hand side for backup or
	      primary MX domain entries.

       Postfix	version  2.2  and  later will not use the fallback_relay feature for destinations
       that it is MX host for.

fallback_transport (default: empty)
       Optional message delivery transport that the local(8) delivery agent should use for  names
       that are not found in the aliases(5) or UNIX password database.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,   mail_spool_directory,   fallback_transport_maps,   fallback_transport  and
       luser_relay.

fallback_transport_maps (default: empty)
       Optional lookup tables with per-recipient message delivery transports for recipients  that
       the local(8) delivery agent could not find in the aliases(5) or UNIX password database.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,   mail_spool_directory,   fallback_transport_maps,   fallback_transport  and
       luser_relay.

       For safety reasons, this feature does not allow $number substitutions in  regular  expres-
       sion maps.

       This feature is available in Postfix 2.3 and later.

fast_flush_domains (default: $relay_domains)
       Optional  list  of  destinations  that are eligible for per-destination logfiles with mail
       that is queued to those destinations.

       By default, Postfix maintains "fast flush" logfiles only for destinations that the Postfix
       SMTP  server  is  willing  to  relay  to  (i.e.	the  default  is:  "fast_flush_domains	=
       $relay_domains"; see the relay_domains parameter in the postconf(5) manual).

       Specify a list of hosts or domains, "/file/name" patterns or "type:table"  lookup  tables,
       separated by commas and/or whitespace.  Continue long lines by starting the next line with
       whitespace. A "/file/name" pattern is replaced by its contents; a "type:table" lookup  ta-
       ble is matched when the domain or its parent domain appears as lookup key.

       Specify "fast_flush_domains =" (i.e., empty) to disable the feature altogether.

fast_flush_purge_time (default: 7d)
       The time after which an empty per-destination "fast flush" logfile is deleted.

       You  can  specify the time as a number, or as a number followed by a letter that indicates
       the time unit: s=seconds, m=minutes, h=hours, d=days, w=weeks.  The default time  unit  is
       days.

fast_flush_refresh_time (default: 12h)
       The  time after which a non-empty but unread per-destination "fast flush" logfile needs to
       be refreshed.  The contents of a logfile are refreshed by requesting delivery of all  mes-
       sages listed in the logfile.

       You  can  specify the time as a number, or as a number followed by a letter that indicates
       the time unit: s=seconds, m=minutes, h=hours, d=days, w=weeks.  The default time  unit  is
       hours.

fault_injection_code (default: 0)
       Force  specific	internal tests to fail, to test the handling of errors that are difficult
       to reproduce otherwise.

flush_service_name (default: flush)
       The name of the flush(8) service. This service maintains per-destination logfiles with the
       queue file names of mail that is queued for those destinations.

       This feature is available in Postfix 2.0 and later.

fork_attempts (default: 5)
       The maximal number of attempts to fork() a child process.

fork_delay (default: 1s)
       The delay between attempts to fork() a child process.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

forward_expansion_filter (default: see postconf -d output)
       Restrict the characters that the local(8) delivery agent allows	in  $name  expansions  of
       $forward_path.  Characters outside the allowed set are replaced by underscores.

forward_path (default: see postconf -d output)
       The  local(8)  delivery	agent search list for finding a .forward file with user-specified
       delivery methods. The first file that is found is used.

       The following $name expansions are done on forward_path before the  search  actually  hap-
       pens.  The  result of $name expansion is filtered with the character set that is specified
       with the forward_expansion_filter parameter.

       $user  The recipient's username.

       $shell The recipient's login shell pathname.

       $home  The recipient's home directory.

       $recipient
	      The full recipient address.

       $extension
	      The optional recipient address extension.

       $domain
	      The recipient domain.

       $local The entire recipient localpart.

       $recipient_delimiter
	      The system-wide recipient address extension delimiter.

       ${name?value}
	      Expands to value when $name is non-empty.

       ${name:value}
	      Expands to value when $name is empty.

       Instead of $name you can also specify ${name} or $(name).

       Examples:

       forward_path = /var/forward/$user
       forward_path =
	   /var/forward/$user/.forward$recipient_delimiter$extension,
	   /var/forward/$user/.forward

frozen_delivered_to (default: yes)
       Update the local(8) delivery agent's idea of the Delivered-To: address (see prepend_deliv-
       ered_header)  only  once, at the start of a delivery attempt; do not update the Delivered-
       To: address while expanding aliases or .forward files.

       This feature is available in Postfix 2.3 and  later.  With  older  Postfix  releases,  the
       behavior  is  as  if  this parameter is set to "no". The old setting can be expensive with
       deeply nested aliases or .forward files. When an alias or .forward file changes the Deliv-
       ered-To: address, it ties up one queue file and one cleanup process instance while mail is
       being forwarded.

hash_queue_depth (default: 1)
       The number of subdirectory levels for queue directories listed with  the  hash_queue_names
       parameter.

       After  changing	the  hash_queue_names  or hash_queue_depth parameter, execute the command
       "postfix reload".

hash_queue_names (default: deferred, defer)
       The names of queue directories that are split across multiple subdirectory levels.

       Before Postfix version 2.2, the default list of hashed queues  was  significantly  larger.
       Claims  about  improvements in file system technology suggest that hashing of the incoming
       and active queues is no longer needed. Fewer hashed directories speed up the  time  needed
       to restart Postfix.

       After  changing	the  hash_queue_names  or hash_queue_depth parameter, execute the command
       "postfix reload".

header_address_token_limit (default: 10240)
       The maximal number of address tokens are allowed in an address message header. Information
       that exceeds the limit is discarded.  The limit is enforced by the cleanup(8) server.

header_checks (default: empty)
       Optional  lookup  tables  for  content  inspection of primary non-MIME message headers, as
       specified in the header_checks(5) manual page.

header_size_limit (default: 102400)
       The maximal amount of memory in bytes for storing  a  message  header.	If  a  header  is
       larger, the excess is discarded.  The limit is enforced by the cleanup(8) server.

helpful_warnings (default: yes)
       Log warnings about problematic configuration settings, and provide helpful suggestions.

       This feature is available in Postfix 2.0 and later.

home_mailbox (default: empty)
       Optional pathname of a mailbox file relative to a local(8) user's home directory.

       Specify a pathname ending in "/" for qmail-style delivery.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,   mail_spool_directory,   fallback_transport_maps,   fallback_transport  and
       luser_relay.

       Examples:

       home_mailbox = Mailbox
       home_mailbox = Maildir/

hopcount_limit (default: 50)
       The maximal number of Received:	message headers that is allowed in  the  primary  message
       headers. A message that exceeds the limit is bounced, in order to stop a mailer loop.

html_directory (default: see postconf -d output)
       The location of Postfix HTML files that describe how to build, configure or operate a spe-
       cific Postfix subsystem or feature.

ignore_mx_lookup_error (default: no)
       Ignore DNS MX lookups that produce no response.	 By  default,  the  Postfix  SMTP  client
       defers  delivery  and tries again after some delay.  This behavior is required by the SMTP
       standard.

       Specify "ignore_mx_lookup_error = yes" to force a DNS A record lookup instead.  This  vio-
       lates the SMTP standard and can result in mis-delivery of mail.

import_environment (default: see postconf -d output)
       The  list  of environment parameters that a Postfix process will import from a non-Postfix
       parent process. Examples of relevant parameters:

       TZ     Needed for sane time keeping on most System-V-ish systems.

       DISPLAY
	      Needed for debugging Postfix daemons with an X-windows debugger.

       XAUTHORITY
	      Needed for debugging Postfix daemons with an X-windows debugger.

       MAIL_CONFIG
	      Needed to make "postfix -c" work.

       Specify a list of names and/or name=value pairs, separated by  whitespace  or  comma.  The
       name=value form is supported with Postfix version 2.1 and later.

in_flow_delay (default: 1s)
       Time  to  pause	before accepting a new message, when the message arrival rate exceeds the
       message delivery rate. This feature is turned on by default (it's disabled on SCO UNIX due
       to an SCO bug).

       With  the  default  100	SMTP  server  process limit, "in_flow_delay = 1s" limits the mail
       inflow to 100 messages per second above the number of messages delivered per second.

       Specify 0 to disable the feature. Valid delays are 0..10.

inet_interfaces (default: all)
       The network interface addresses that this mail system receives mail on. Specify	"all"  to
       receive	mail  on all network interfaces (default), and "loopback-only" to receive mail on
       loopback network interfaces only (Postfix version 2.2 and later).  The parameter also con-
       trols delivery of mail to user@[ip.address].

       Note 1: you need to stop and start Postfix when this parameter changes.

       Note 2: address information may be enclosed inside [], but this form is not required here.

       When  inet_interfaces  specifies  just one IPv4 and/or IPv6 address that is not a loopback
       address, the Postfix SMTP client will use this address as the IP source address	for  out-
       bound mail. Support for IPv6 is available in Postfix version 2.2 and later.

       On  a  multi-homed  firewall with separate Postfix instances listening on the "inside" and
       "outside" interfaces, this can prevent each instance from being able to reach  servers  on
       the  "other  side" of the firewall. Setting smtp_bind_address to 0.0.0.0 avoids the poten-
       tial problem for IPv4, and setting smtp_bind_address6 to :: solves the problem for IPv6.

       A better solution for multi-homed firewalls is to leave	inet_interfaces  at  the  default
       value  and  instead  use  explicit  IP addresses in the master.cf SMTP server definitions.
       This preserves the Postfix SMTP client's loop detection, by ensuring that each side of the
       firewall  knows that the other IP address is still the same host. Setting $inet_interfaces
       to a single IPv4 and/or IPV6 address is primarily useful with virtual hosting  of  domains
       on  secondary IP addresses, when each IP address serves a different domain (and has a dif-
       ferent $myhostname setting).

       See also the proxy_interfaces parameter, for network addresses that are forwarded to Post-
       fix by way of a proxy or address translator.

       Examples:

       inet_interfaces = all (DEFAULT)
       inet_interfaces = loopback-only (Postfix version 2.2 and later)
       inet_interfaces = 127.0.0.1
       inet_interfaces = 127.0.0.1, [::1] (Postfix version 2.2 and later)
       inet_interfaces = 192.168.1.2, 127.0.0.1

inet_protocols (default: ipv4)
       The  Internet  protocols Postfix will attempt to use when making or accepting connections.
       Specify one or more of "ipv4" or "ipv6", separated by whitespace or commas. The form "all"
       is  equivalent to "ipv4, ipv6" or "ipv4", depending on whether the operating system imple-
       ments IPv6.

       This feature is available in Postfix 2.2 and later.

       Note: you MUST stop and start Postfix after changing this parameter.

       On systems that pre-date IPV6_V6ONLY support (RFC 3493), an IPv6 server will  also  accept
       IPv4 connections, even when IPv4 is turned off with the inet_protocols parameter.  On sys-
       tems with IPV6_V6ONLY support, Postfix will use separate server sockets for IPv6 and IPv4,
       and each will accept only connections for the corresponding protocol.

       When  IPv4 support is enabled via the inet_protocols parameter, Postfix will to DNS type A
       record lookups, and will convert IPv4-in-IPv6  client  IP  addresses  (::ffff:1.2.3.4)  to
       their  original	IPv4  form  (1.2.3.4).	 The  latter  is  needed  on  hosts that pre-date
       IPV6_V6ONLY support (RFC 3493).

       When IPv6 support is enabled via the inet_protocols parameter, Postfix will  do	DNS  type
       AAAA record lookups.

       When  both IPv4 and IPv6 support are enabled, the Postfix SMTP client will attempt to con-
       nect via IPv6 before attempting to use IPv4.

       Examples:

       inet_protocols = ipv4 (DEFAULT)
       inet_protocols = all
       inet_protocols = ipv6
       inet_protocols = ipv4, ipv6

initial_destination_concurrency (default: 5)
       The initial per-destination concurrency level for parallel delivery to the  same  destina-
       tion.   With  per-destination recipient limit > 1, a destination is a domain, otherwise it
       is a recipient.

       Use transport_initial_destination_concurrency to specify  a  transport-specific	override,
       where  transport  is the master.cf name of the message delivery transport (Postfix 2.5 and
       later).

       Warning: with concurrency of 1, one bad message can be enough to block all mail to a site.

internal_mail_filter_classes (default: empty)
       What categories of Postfix-generated mail are subject to before-queue  content  inspection
       by  non_smtpd_milters, header_checks and body_checks.  Specify zero or more of the follow-
       ing, separated by whitespace or comma.

       bounce Inspect the content of delivery status notifications.

       notify Inspect the content of postmaster notifications by the smtp(8)  and  smtpd(8)  pro-
	      cesses.

       NOTE: It's generally not safe to enable content inspection of Postfix-generated email mes-
       sages. The user is warned.

       This feature is available in Postfix 2.3 and later.

invalid_hostname_reject_code (default: 501)
       The numerical Postfix SMTP server response code when  the  client  HELO	or  EHLO  command
       parameter is rejected by the reject_invalid_helo_hostname restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

ipc_idle (default: version dependent)
       The  time after which a client closes an idle internal communication channel.  The purpose
       is to allow servers to terminate voluntarily after they become idle.  This  is  used,  for
       example, by the address resolving and rewriting clients.

       With Postfix 2.4 the default value was reduced from 100s to 5s.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

ipc_timeout (default: 3600s)
       The time limit for sending or receiving information over an internal  communication  chan-
       nel.   The  purpose  is to break out of deadlock situations. If the time limit is exceeded
       the software aborts with a fatal error.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

ipc_ttl (default: 1000s)
       The  time  after which a client closes an active internal communication channel.  The pur-
       pose is to allow servers to terminate voluntarily after reaching their client limit.  This
       is used, for example, by the address resolving and rewriting clients.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1 and later.

line_length_limit (default: 2048)
       Upon input, long lines are chopped up into pieces of at most this length;  upon	delivery,
       long lines are reconstructed.

lmtp_address_preference (default: ipv6)
       The  LMTP-specific  version  of	the smtp_address_preference configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.8 and later.

lmtp_assume_final (default: no)
       When an LMTP server announces no DSN support, assume that the server performs final deliv-
       ery,  and send "delivered" delivery status notifications instead of "relayed". The default
       setting is backwards compatible to avoid the infinetisimal possibility of breaking  exist-
       ing LMTP-based content filters.

lmtp_bind_address (default: empty)
       The LMTP-specific version of the smtp_bind_address configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_bind_address6 (default: empty)
       The LMTP-specific version of the smtp_bind_address6 configuration  parameter.   See  there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_body_checks (default: empty)
       The  LMTP-specific  version of the smtp_body_checks configuration parameter. See there for
       details.

       This feature is available in Postfix 2.5 and later.

lmtp_cache_connection (default: yes)
       Keep Postfix LMTP client connections open for up  to  $max_idle	seconds.  When	the  LMTP
       client receives a request for the same connection the connection is reused.

       This  parameter is available in Postfix version 2.2 and earlier.  With Postfix version 2.3
       and later,  see	lmtp_connection_cache_on_demand,  lmtp_connection_cache_destinations,  or
       lmtp_connection_reuse_time_limit.

       The  effectiveness  of cached connections will be determined by the number of LMTP servers
       in use, and the concurrency limit specified for the LMTP client.  Cached  connections  are
       closed under any of the following conditions:

       o      The LMTP client idle time limit is reached.  This limit is specified with the Post-
	      fix max_idle configuration parameter.

       o      A delivery request specifies a different destination than the one currently cached.

       o      The per-process limit on the number of delivery requests is reached.  This limit is
	      specified with the Postfix max_use configuration parameter.

       o      Upon  the  onset	of  another delivery request, the LMTP server associated with the
	      current session does not respond to the RSET command.

       Most of these limitations will be removed after Postfix implements a connection cache that
       is shared among multiple LMTP client programs.

lmtp_cname_overrides_servername (default: yes)
       The  LMTP-specific version of the smtp_cname_overrides_servername configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_connect_timeout (default: 0s)
       The LMTP client time limit for completing a TCP connection, or  zero  (use  the	operating
       system built-in time limit).  When no connection can be made within the deadline, the LMTP
       client tries the next address on the mail exchanger list.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

       Example:

       lmtp_connect_timeout = 30s

lmtp_connection_cache_destinations (default: empty)
       The  LMTP-specific version of the smtp_connection_cache_destinations configuration parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_connection_cache_on_demand (default: yes)
       The LMTP-specific version of the smtp_connection_cache_on_demand configuration  parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_connection_cache_time_limit (default: 2s)
       The LMTP-specific version of the smtp_connection_cache_time_limit configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_connection_reuse_time_limit (default: 300s)
       The LMTP-specific version of the smtp_connection_reuse_time_limit configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_data_done_timeout (default: 600s)
       The  LMTP  client  time	limit  for  sending  the  LMTP	".", and for receiving the server
       response.  When no response is received within the deadline, a warning is logged that  the
       mail may be delivered multiple times.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_data_init_timeout (default: 120s)
       The LMTP client time limit for sending the LMTP DATA command, and for receiving the server
       response.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_data_xfer_timeout (default: 180s)
       The LMTP client time limit for sending the LMTP	message  content.   When  the  connection
       stalls for more than $lmtp_data_xfer_timeout the LMTP client terminates the transfer.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_defer_if_no_mx_address_found (default: no)
       The LMTP-specific version of the smtp_defer_if_no_mx_address_found  configuration  parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_destination_concurrency_limit (default: $default_destination_concurrency_limit)
       The  maximal  number  of  parallel deliveries to the same destination via the lmtp message
       delivery transport. This limit is enforced by the  queue  manager.  The	message  delivery
       transport name is the first field in the entry in the master.cf file.

lmtp_destination_recipient_limit (default: $default_destination_recipient_limit)
       The maximal number of recipients per message for the lmtp message delivery transport. This
       limit is enforced by the queue manager. The message delivery transport name is  the  first
       field in the entry in the master.cf file.

       Setting	this  parameter  to  a value of 1 changes the meaning of lmtp_destination_concur-
       rency_limit from concurrency per domain into concurrency per recipient.

lmtp_discard_lhlo_keyword_address_maps (default: empty)
       Lookup tables, indexed by the remote LMTP server address, with case insensitive	lists  of
       LHLO  keywords  (pipelining, starttls, auth, etc.) that the LMTP client will ignore in the
       LHLO response from a remote LMTP server. See lmtp_discard_lhlo_keywords for  details.  The
       table   is   not   indexed   by	hostname  for  consistency  with  smtpd_discard_ehlo_key-
       word_address_maps.

       This feature is available in Postfix 2.3 and later.

lmtp_discard_lhlo_keywords (default: empty)
       A case insensitive list of LHLO keywords (pipelining, starttls, auth, etc.) that the  LMTP
       client will ignore in the LHLO response from a remote LMTP server.

       This feature is available in Postfix 2.3 and later.

       Notes:

       o      Specify the silent-discard pseudo keyword to prevent this action from being logged.

       o      Use  the	lmtp_discard_lhlo_keyword_address_maps	feature  to discard LHLO keywords
	      selectively.

lmtp_dns_resolver_options (default: empty)
       The LMTP-specific version of the smtp_dns_resolver_options configuration  parameter.   See
       there for details.

       This feature is available in Postfix 2.8 and later.

lmtp_enforce_tls (default: no)
       The  LMTP-specific version of the smtp_enforce_tls configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_generic_maps (default: empty)
       The LMTP-specific version of the smtp_generic_maps configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_header_checks (default: empty)
       The LMTP-specific version of the smtp_header_checks configuration parameter. See there for
       details.

       This feature is available in Postfix 2.5 and later.

lmtp_host_lookup (default: dns)
       The LMTP-specific version of the smtp_host_lookup configuration parameter.  See there  for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_lhlo_name (default: $myhostname)
       The hostname to send in the LMTP LHLO command.

       The default value is the machine hostname.  Specify a hostname or [ip.add.re.ss].

       This  information  can be specified in the main.cf file for all LMTP clients, or it can be
       specified in the master.cf file for a specific client, for example:

	   /etc/postfix/master.cf:
	       mylmtp ... lmtp -o lmtp_lhlo_name=foo.bar.com

       This feature is available in Postfix 2.3 and later.

lmtp_lhlo_timeout (default: 300s)
       The LMTP client time limit for sending the LHLO command, and  for  receiving  the  initial
       server response.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_line_length_limit (default: 990)
       The LMTP-specific version of  the  smtp_line_length_limit  configuration  parameter.   See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_mail_timeout (default: 300s)
       The LMTP client time limit for sending the MAIL FROM command, and for receiving the server
       response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

lmtp_mime_header_checks (default: empty)
       The  LMTP-specific  version  of	the  smtp_mime_header_checks configuration parameter. See
       there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_mx_address_limit (default: 5)
       The LMTP-specific version of the smtp_mx_address_limit configuration parameter.	See there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_mx_session_limit (default: 2)
       The LMTP-specific version of the smtp_mx_session_limit configuration parameter.	See there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_nested_header_checks (default: empty)
       The LMTP-specific version of the smtp_nested_header_checks  configuration  parameter.  See
       there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_pix_workaround_delay_time (default: 10s)
       The  LMTP-specific  version of the smtp_pix_workaround_delay_time configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_pix_workaround_maps (default: empty)
       The LMTP-specific version of the smtp_pix_workaround_maps  configuration  parameter.   See
       there for details.

       This feature is available in Postfix 2.4 and later.

lmtp_pix_workaround_threshold_time (default: 500s)
       The  LMTP-specific version of the smtp_pix_workaround_threshold_time configuration parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_pix_workarounds (default: empty)
       The LMTP-specific version of the smtp_pix_workaround configuration parameter.   See  there
       for details.

       This feature is available in Postfix 2.4 and later.

lmtp_quit_timeout (default: 300s)
       The  LMTP  client  time	limit  for sending the QUIT command, and for receiving the server
       response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

lmtp_quote_rfc821_envelope (default: yes)
       The  LMTP-specific version of the smtp_quote_rfc821_envelope configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_randomize_addresses (default: yes)
       The LMTP-specific version of the smtp_randomize_addresses  configuration  parameter.   See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_rcpt_timeout (default: 300s)
       The  LMTP  client time limit for sending the RCPT TO command, and for receiving the server
       response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

lmtp_reply_filter (default: empty)
       The LMTP-specific version of the smtp_reply_filter configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.7 and later.

lmtp_rset_timeout (default: 20s)
       The LMTP client time limit for sending the RSET command,  and  for  receiving  the  server
       response.  The  LMTP client sends RSET in order to finish a recipient address probe, or to
       verify that a cached connection is still alive.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

lmtp_sasl_auth_cache_name (default: empty)
       The  LMTP-specific  version of the smtp_sasl_auth_cache_name configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_sasl_auth_cache_time (default: 90d)
       The LMTP-specific version of the smtp_sasl_auth_cache_time configuration  parameter.   See
       there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_sasl_auth_enable (default: no)
       Enable SASL authentication in the Postfix LMTP client.

lmtp_sasl_auth_soft_bounce (default: yes)
       The  LMTP-specific version of the smtp_sasl_auth_soft_bounce configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_sasl_mechanism_filter (default: empty)
       The LMTP-specific version of the smtp_sasl_mechanism_filter configuration parameter.   See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_sasl_password_maps (default: empty)
       Optional  LMTP  client  lookup tables with one username:password entry per host or domain.
       If a remote host or domain has no username:password entry, then the  Postfix  LMTP  client
       will not attempt to authenticate to the remote host.

lmtp_sasl_path (default: empty)
       Implementation-specific information that is passed through to the SASL plug-in implementa-
       tion that is selected with lmtp_sasl_type.  Typically this specifies the name of a config-
       uration file or rendezvous point.

       This feature is available in Postfix 2.3 and later.

lmtp_sasl_security_options (default: noplaintext, noanonymous)
       SASL  security  options;  as  of Postfix 2.3 the list of available features depends on the
       SASL client implementation that is selected with lmtp_sasl_type.

       The following security features are defined for the cyrus client SASL implementation:

       noplaintext
	      Disallow authentication methods that use plaintext passwords.

       noactive
	      Disallow authentication  methods	that  are  vulnerable  to  non-dictionary  active
	      attacks.

       nodictionary
	      Disallow authentication methods that are vulnerable to passive dictionary attack.

       noanonymous
	      Disallow anonymous logins.

       Example:

       lmtp_sasl_security_options = noplaintext

lmtp_sasl_tls_security_options (default: $lmtp_sasl_security_options)
       The  LMTP-specific  version of the smtp_sasl_tls_security_options configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_sasl_tls_verified_security_options (default: $lmtp_sasl_tls_security_options)
       The LMTP-specific version  of  the  smtp_sasl_tls_verified_security_options  configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_sasl_type (default: cyrus)
       The  SASL  plug-in  type  that the Postfix LMTP client should use for authentication.  The
       available types are listed with the "postconf -A" command.

       This feature is available in Postfix 2.3 and later.

lmtp_send_xforward_command (default: no)
       Send an XFORWARD command to the LMTP server when the LMTP LHLO server  response	announces
       XFORWARD  support.  This allows an lmtp(8) delivery agent, used for content filter message
       injection, to forward the name, address, protocol and HELO name of the original client  to
       the  content  filter  and  downstream queuing LMTP server.  Before you change the value to
       yes, it is best to make sure that your content filter supports this command.

       This feature is available in Postfix 2.1 and later.

lmtp_sender_dependent_authentication (default: no)
       The LMTP-specific version of the smtp_sender_dependent_authentication configuration param-
       eter.  See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_skip_5xx_greeting (default: yes)
       The  LMTP-specific  version  of	the  smtp_skip_5xx_greeting configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_skip_quit_response (default: no)
       Wait for the response to the LMTP QUIT command.

lmtp_starttls_timeout (default: 300s)
       The LMTP-specific version of the smtp_starttls_timeout configuration parameter.	See there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tcp_port (default: 24)
       The default TCP port that the Postfix LMTP client connects to.

lmtp_tls_CAfile (default: empty)
       The  LMTP-specific  version of the smtp_tls_CAfile configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_CApath (default: empty)
       The LMTP-specific version of the smtp_tls_CApath configuration parameter.  See  there  for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_block_early_mail_reply (default: empty)
       The  LMTP-specific version of the smtp_tls_block_early_mail_reply configuration parameter.
       See there for details.

       This feature is available in Postfix 2.7 and later.

lmtp_tls_cert_file (default: empty)
       The LMTP-specific version of the smtp_tls_cert_file configuration  parameter.   See  there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_ciphers (default: export)
       The  LMTP-specific  version of the smtp_tls_ciphers configuration parameter. See there for
       details.

       This feature is available in Postfix 2.6 and later.

lmtp_tls_dcert_file (default: empty)
       The LMTP-specific version of the smtp_tls_dcert_file configuration parameter.   See  there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_dkey_file (default: $lmtp_tls_dcert_file)
       The  LMTP-specific  version  of the smtp_tls_dkey_file configuration parameter.	See there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_eccert_file (default: empty)
       The LMTP-specific version of the smtp_tls_eccert_file configuration parameter.  See  there
       for details.

       This  feature  is  available in Postfix 2.6 and later, when Postfix is compiled and linked
       with OpenSSL 1.0.0 or later.

lmtp_tls_eckey_file (default: empty)
       The LMTP-specific version of the smtp_tls_eckey_file configuration parameter.   See  there
       for details.

       This  feature  is  available in Postfix 2.6 and later, when Postfix is compiled and linked
       with OpenSSL 1.0.0 or later.

lmtp_tls_enforce_peername (default: yes)
       The LMTP-specific version of the smtp_tls_enforce_peername configuration  parameter.   See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_exclude_ciphers (default: empty)
       The  LMTP-specific  version  of the smtp_tls_exclude_ciphers configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_fingerprint_cert_match (default: empty)
       The LMTP-specific version of the smtp_tls_fingerprint_cert_match configuration  parameter.
       See there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_tls_fingerprint_digest (default: md5)
       The LMTP-specific version of the smtp_tls_fingerprint_digest configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.5 and later.

lmtp_tls_key_file (default: $lmtp_tls_cert_file)
       The LMTP-specific version of the smtp_tls_key_file configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_loglevel (default: 0)
       The LMTP-specific version of the smtp_tls_loglevel configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_mandatory_ciphers (default: empty)
       The LMTP-specific version of the smtp_tls_mandatory_ciphers configuration parameter.   See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_mandatory_exclude_ciphers (default: empty)
       The  LMTP-specific version of the smtp_tls_mandatory_exclude_ciphers configuration parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_mandatory_protocols (default: !SSLv2)
       The LMTP-specific version of the smtp_tls_mandatory_protocols configuration parameter. See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_note_starttls_offer (default: no)
       The  LMTP-specific  version  of	the smtp_tls_note_starttls_offer configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_per_site (default: empty)
       The LMTP-specific version of the smtp_tls_per_site configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_policy_maps (default: empty)
       The  LMTP-specific  version of the smtp_tls_policy_maps configuration parameter. See there
       for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_protocols (default: empty)
       The LMTP-specific version of the smtp_tls_protocols configuration parameter. See there for
       details.

       This feature is available in Postfix 2.6 and later.

lmtp_tls_scert_verifydepth (default: 9)
       The  LMTP-specific version of the smtp_tls_scert_verifydepth configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_secure_cert_match (default: nexthop)
       The LMTP-specific version of the smtp_tls_secure_cert_match configuration  parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_security_level (default: empty)
       The  LMTP-specific  version  of	the smtp_tls_security_level configuration parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_session_cache_database (default: empty)
       The LMTP-specific version of the smtp_tls_session_cache_database configuration  parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_session_cache_timeout (default: 3600s)
       The  LMTP-specific  version of the smtp_tls_session_cache_timeout configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_tls_verify_cert_match (default: hostname)
       The LMTP-specific version of the smtp_tls_verify_cert_match configuration  parameter.  See
       there for details.

       This feature is available in Postfix 2.3 and later.

lmtp_use_tls (default: no)
       The  LMTP-specific  version  of	the  smtp_use_tls configuration parameter.  See there for
       details.

       This feature is available in Postfix 2.3 and later.

lmtp_xforward_timeout (default: 300s)
       The LMTP client time limit for sending the XFORWARD command, and for receiving the  server
       response.

       In case of problems the client does NOT try the next address on the mail exchanger list.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1 and later.

local_command_shell (default: empty)
       Optional shell program for local(8) delivery to non-Postfix  command.   By  default,  non-
       Postfix	commands  are executed directly; commands are given to given to the default shell
       (typically, /bin/sh) only when they contain shell meta characters or shell  built-in  com-
       mands.

       "sendmail's  restricted	shell"	(smrsh) is what most people will use in order to restrict
       what programs can be run from e.g. .forward files (smrsh is part of the Sendmail distribu-
       tion).

       Note:  when  a shell program is specified, it is invoked even when the command contains no
       shell built-in commands or meta characters.

       Example:

       local_command_shell = /some/where/smrsh -c
       local_command_shell = /bin/bash -c

local_destination_concurrency_limit (default: 2)
       The maximal number of parallel deliveries via the local mail  delivery  transport  to  the
       same  recipient	(when  "local_destination_recipient_limit  = 1") or the maximal number of
       parallel deliveries to the same local domain  (when  "local_destination_recipient_limit	>
       1").  This  limit is enforced by the queue manager. The message delivery transport name is
       the first field in the entry in the master.cf file.

       A low limit of 2 is recommended, just in case someone has an expensive shell command in	a
       .forward  file  or in an alias (e.g., a mailing list manager).  You don't want to run lots
       of those at the same time.

local_destination_recipient_limit (default: 1)
       The maximal number of recipients per message delivery via the local mail  delivery  trans-
       port.  This limit is enforced by the queue manager. The message delivery transport name is
       the first field in the entry in the master.cf file.

       Setting this parameter to a value > 1 changes  the  meaning  of	local_destination_concur-
       rency_limit from concurrency per recipient into concurrency per domain.

local_header_rewrite_clients (default: permit_inet_interfaces)
       Rewrite	message  header  addresses  in	mail  from  these  clients  and update incomplete
       addresses with the domain name in $myorigin or $mydomain;  either  don't  rewrite  message
       headers	from  other  clients  at  all,	or  rewrite message headers and update incomplete
       addresses with the domain specified in the remote_header_rewrite_domain parameter.

       See the append_at_myorigin and append_dot_mydomain parameters for details  of  how  domain
       names are appended to incomplete addresses.

       Specify a list of zero or more of the following:

       permit_inet_interfaces
	      Append the domain name in $myorigin or $mydomain when the client IP address matches
	      $inet_interfaces. This is enabled by default.

       permit_mynetworks
	      Append the domain name in $myorigin or $mydomain when the client IP address matches
	      any network or network address listed in $mynetworks. This setting will not prevent
	      remote mail header address rewriting when mail from a remote client is forwarded by
	      a neighboring system.

       permit_sasl_authenticated
	      Append  the  domain  name in $myorigin or $mydomain when the client is successfully
	      authenticated via the RFC 4954 (AUTH) protocol.

       permit_tls_clientcerts
	      Append the domain name in $myorigin or $mydomain when the  client  TLS  certificate
	      fingerprint  is  listed in $relay_clientcerts.  The fingerprint digest algorithm is
	      configurable via the  smtpd_tls_fingerprint_digest  parameter  (hard-coded  as  md5
	      prior to Postfix version 2.5).

       permit_tls_all_clientcerts
	      Append the domain name in $myorigin or $mydomain when the client TLS certificate is
	      successfully verified, regardless of whether  it	is  listed  on	the  server,  and
	      regardless of the certifying authority.

       check_address_map type:table

       type:table
	      Append the domain name in $myorigin or $mydomain when the client IP address matches
	      the specified lookup table.  The lookup result is ignored, and no subnet lookup  is
	      done. This is suitable for, e.g., pop-before-smtp lookup tables.

       Examples:

       The Postfix < 2.2 backwards compatible setting: always rewrite message headers, and always
       append my own domain to incomplete header addresses.

	   local_header_rewrite_clients = static:all

       The purist (and default) setting: rewrite headers only in mail from Postfix  sendmail  and
       in SMTP mail from this machine.

	   local_header_rewrite_clients = permit_inet_interfaces

       The  intermediate  setting:  rewrite  header  addresses	and append $myorigin or $mydomain
       information only with mail from Postfix sendmail, from local clients, or  from  authorized
       SMTP clients.

       Note:  this setting will not prevent remote mail header address rewriting when mail from a
       remote client is forwarded by a neighboring system.

	   local_header_rewrite_clients = permit_mynetworks,
	       permit_sasl_authenticated permit_tls_clientcerts
	       check_address_map hash:/etc/postfix/pop-before-smtp

local_recipient_maps (default: proxy:unix:passwd.byname $alias_maps)
       Lookup tables with all names or addresses of local  recipients:	a  recipient  address  is
       local  when  its  domain  matches  $mydestination,  $inet_interfaces or $proxy_interfaces.
       Specify @domain as a wild-card for domains that do not have a valid recipient list.  Tech-
       nically, tables listed with $local_recipient_maps are used as lists: Postfix needs to know
       only if a lookup string is found or not, but it does not use the result from table lookup.

       If this parameter is non-empty (the default), then the Postfix  SMTP  server  will  reject
       mail for unknown local users.

       To  turn  off  local recipient checking in the Postfix SMTP server, specify "local_recipi-
       ent_maps =" (i.e. empty).

       The default setting assumes that you use the default  Postfix  local  delivery  agent  for
       local delivery. You need to update the local_recipient_maps setting if:

       o      You redefine the local delivery agent in master.cf.

       o      You redefine the "local_transport" setting in main.cf.

       o      You  use the "luser_relay", "mailbox_transport", or "fallback_transport" feature of
	      the Postfix local(8) delivery agent.

       Details are described in the LOCAL_RECIPIENT_README file.

       Beware: if the Postfix SMTP server runs chrooted, you need to access the passwd	file  via
       the proxymap(8) service, in order to overcome chroot access restrictions. The alternative,
       maintaining a copy of the system password file in the chroot jail is not practical.

       Examples:

       local_recipient_maps =

local_transport (default: local:$myhostname)
       The default mail delivery transport and next-hop destination for final delivery to domains
       listed with mydestination, and for [ipaddress] destinations that match $inet_interfaces or
       $proxy_interfaces.  This information can be overruled with the transport(5) table.

       By default, local mail is delivered to the transport called "local",  which  is	just  the
       name of a service that is defined the master.cf file.

       Specify	a  string  of  the  form transport:nexthop, where transport is the name of a mail
       delivery transport defined in master.cf.  The :nexthop destination is optional; its syntax
       is documented in the manual page of the corresponding delivery agent.

       Beware:	if  you  override  the	default  local delivery agent then you need to review the
       LOCAL_RECIPIENT_README document, otherwise the SMTP  server  may  reject  mail  for  local
       recipients.

luser_relay (default: empty)
       Optional  catch-all  destination  for  unknown  local(8) recipients.  By default, mail for
       unknown recipients in domains that match $mydestination, $inet_interfaces or $proxy_inter-
       faces is returned as undeliverable.

       The following $name expansions are done on luser_relay:

       $domain
	      The recipient domain.

       $extension
	      The recipient address extension.

       $home  The recipient's home directory.

       $local The entire recipient address localpart.

       $recipient
	      The full recipient address.

       $recipient_delimiter
	      The system-wide recipient address extension delimiter.

       $shell The recipient's login shell.

       $user  The recipient username.

       ${name?value}
	      Expands to value when $name has a non-empty value.

       ${name:value}
	      Expands to value when $name has an empty value.

       Instead of $name you can also specify ${name} or $(name).

       Note: luser_relay works only for the Postfix local(8) delivery agent.

       Note:  if  you  use this feature for accounts not in the UNIX password file, then you must
       specify "local_recipient_maps =" (i.e. empty) in the main.cf file, otherwise  the  Postfix
       SMTP  server  will reject mail for non-UNIX accounts with "User unknown in local recipient
       table".

       Examples:

       luser_relay = $user@other.host
       luser_relay = $local@other.host
       luser_relay = admin+$local

mail_name (default: Postfix)
       The mail system name that is displayed in Received: headers, in the SMTP greeting  banner,
       and in bounced mail.

mail_owner (default: postfix)
       The  UNIX  system  account  that owns the Postfix queue and most Postfix daemon processes.
       Specify the name of a user account that does not share a group  with  other  accounts  and
       that  owns no other files or processes on the system.  In particular, don't specify nobody
       or daemon.  PLEASE USE A DEDICATED USER ID AND GROUP ID.

       When this parameter value is changed you need to re-run	"postfix  set-permissions"  (with
       Postfix version 2.0 and earlier: "/etc/postfix/post-install set-permissions".

mail_release_date (default: see postconf -d output)
       The Postfix release date, in "YYYYMMDD" format.

mail_spool_directory (default: see postconf -d output)
       The directory where local(8) UNIX-style mailboxes are kept. The default setting depends on
       the system type. Specify a name ending in / for maildir-style delivery.

       Note: maildir delivery is done with the privileges of  the  recipient.	If  you  use  the
       mail_spool_directory  setting  for  maildir  style delivery, then you must create the top-
       level maildir directory in advance. Postfix will not create it.

       Examples:

       mail_spool_directory = /var/mail
       mail_spool_directory = /var/spool/mail

mail_version (default: see postconf -d output)
       The version of the mail system. Stable releases are named major.minor.patchlevel.  Experi-
       mental  releases  also  include	the  release date. The version string can be used in, for
       example, the SMTP greeting banner.

mailbox_command (default: empty)
       Optional external command that the local(8) delivery agent should use for  mailbox  deliv-
       ery.   The  command  is	run  with  the user ID and the primary group ID privileges of the
       recipient.  Exception: command delivery for root executes with $default_privs  privileges.
       This  is  not  a problem, because 1) mail for root should always be aliased to a real user
       and 2) don't log in as root, use "su" instead.

       The following environment variables are exported to the command:

       CLIENT_ADDRESS
	      Remote client network address. Available in Postfix version 2.2 and later.

       CLIENT_HELO
	      Remote client EHLO command parameter. Available in Postfix version 2.2 and later.

       CLIENT_HOSTNAME
	      Remote client hostname. Available in Postfix version 2.2 and later.

       CLIENT_PROTOCOL
	      Remote client protocol. Available in Postfix version 2.2 and later.

       DOMAIN The domain part of the recipient address.

       EXTENSION
	      The optional address extension.

       HOME   The recipient home directory.

       LOCAL  The recipient address localpart.

       LOGNAME
	      The recipient's username.

       ORIGINAL_RECIPIENT
	      The entire recipient address, before any address rewriting or aliasing.

       RECIPIENT
	      The full recipient address.

       SASL_METHOD
	      SASL authentication method specified in the remote client AUTH  command.	Available
	      in Postfix version 2.2 and later.

       SASL_SENDER
	      SASL  sender address specified in the remote client MAIL FROM command. Available in
	      Postfix version 2.2 and later.

       SASL_USER
	      SASL username specified in the remote client AUTH command.   Available  in  Postfix
	      version 2.2 and later.

       SENDER The full sender address.

       SHELL  The recipient's login shell.

       USER   The recipient username.

       Unlike  other  Postfix configuration parameters, the mailbox_command parameter is not sub-
       jected to $name substitutions. This is to make it easier  to  specify  shell  syntax  (see
       example below).

       If  you	can, avoid shell meta characters because they will force Postfix to run an expen-
       sive shell process. If you're delivering via Procmail then running a shell  won't  make	a
       noticeable difference in the total cost.

       Note:  if you use the mailbox_command feature to deliver mail system-wide, you must set up
       an alias that forwards mail for root to a real user.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,  mail_spool_directory,   fallback_transport_maps,	 fallback_transport   and
       luser_relay.

       Examples:

       mailbox_command = /some/where/procmail
       mailbox_command = /some/where/procmail -a "$EXTENSION"
       mailbox_command = /some/where/maildrop -d "$USER"
	       -f "$SENDER" "$EXTENSION"

mailbox_command_maps (default: empty)
       Optional  lookup  tables  with per-recipient external commands to use for local(8) mailbox
       delivery.  Behavior is as with mailbox_command.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,  mail_spool_directory,   fallback_transport_maps,	 fallback_transport   and
       luser_relay.

mailbox_delivery_lock (default: see postconf -d output)
       How  to	lock  a  UNIX-style  local(8)  mailbox before attempting delivery.  For a list of
       available file locking methods, use the "postconf -l" command.

       This setting is ignored with maildir style delivery,  because  such  deliveries	are  safe
       without explicit locks.

       Note:  The  dotlock  method requires that the recipient UID or GID has write access to the
       parent directory of the mailbox file.

       Note: the default setting of this parameter is system dependent.

mailbox_size_limit (default: 51200000)
       The maximal size of any local(8) individual mailbox or maildir file, or zero  (no  limit).
       In  fact, this limits the size of any file that is written to upon local delivery, includ-
       ing files written by external commands that are executed by the local(8) delivery agent.

       This limit must not be smaller than the message size limit.

mailbox_transport (default: empty)
       Optional message delivery transport that the local(8) delivery agent should use for  mail-
       box  delivery  to  all  local recipients, whether or not they are found in the UNIX passwd
       database.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,  mail_spool_directory,   fallback_transport_maps,	 fallback_transport   and
       luser_relay.

mailbox_transport_maps (default: empty)
       Optional  lookup tables with per-recipient message delivery transports to use for local(8)
       mailbox delivery, whether or not the recipients are found in the UNIX passwd database.

       The precedence of local(8) delivery features from high to low is: aliases, .forward files,
       mailbox_transport_maps,	  mailbox_transport,	mailbox_command_maps,	 mailbox_command,
       home_mailbox,  mail_spool_directory,   fallback_transport_maps,	 fallback_transport   and
       luser_relay.

       For  safety  reasons, this feature does not allow $number substitutions in regular expres-
       sion maps.

       This feature is available in Postfix 2.3 and later.

mailq_path (default: see postconf -d output)
       Sendmail compatibility feature that  specifies  where  the  Postfix  mailq(1)  command  is
       installed. This command can be used to list the Postfix mail queue.

manpage_directory (default: see postconf -d output)
       Where the Postfix manual pages are installed.

maps_rbl_domains (default: empty)
       Obsolete feature: use the reject_rbl_client feature instead.

maps_rbl_reject_code (default: 554)
       The  numerical  Postfix	SMTP  server  response	code when a remote SMTP client request is
       blocked	by  the  reject_rbl_client,   reject_rhsbl_client,   reject_rhsbl_reverse_client,
       reject_rhsbl_sender or reject_rhsbl_recipient restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

masquerade_classes (default: envelope_sender, header_sender, header_recipient)
       What addresses are subject to address masquerading.

       By  default,  address  masquerading is limited to envelope sender addresses, and to header
       sender and header recipient addresses.  This allows you to use address masquerading  on	a
       mail gateway while still being able to forward mail to users on individual machines.

       Specify zero or more of: envelope_sender, envelope_recipient, header_sender, header_recip-
       ient

masquerade_domains (default: empty)
       Optional list of  domains  whose  subdomain  structure  will  be  stripped  off	in  email
       addresses.

       The list is processed left to right, and processing stops at the first match.  Thus,

	   masquerade_domains = foo.example.com example.com

       strips	 "user@any.thing.foo.example.com"    to    "user@foo.example.com",   but   strips
       "user@any.thing.else.example.com" to "user@example.com".

       A domain name prefixed with ! means do not masquerade this domain or its subdomains. Thus,

	   masquerade_domains = !foo.example.com example.com

       does not change "user@any.thing.foo.example.com"  or  "user@foo.example.com",  but  strips
       "user@any.thing.else.example.com" to "user@example.com".

       Note: with Postfix version 2.2, message header address masquerading happens only when mes-
       sage header address rewriting is enabled:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received  from  a	network  client  that  matches	$local_header_re-
	      write_clients,

       o      The  message  is	received  from	the network, and the remote_header_rewrite_domain
	      parameter specifies a non-empty value.

       To get the behavior before Postfix version 2.2,	specify  "local_header_rewrite_clients	=
       static:all".

       Example:

       masquerade_domains = $mydomain

masquerade_exceptions (default: empty)
       Optional  list  of  user  names	that are not subjected to address masquerading, even when
       their address matches $masquerade_domains.

       By default, address masquerading makes no exceptions.

       Specify a list of user names, "/file/name" or "type:table" patterns, separated  by  commas
       and/or  whitespace.  The  list is matched left to right, and the search stops on the first
       match. A "/file/name" pattern is replaced by its contents; a "type:table" lookup table  is
       matched	when  a  name matches a lookup key (the lookup result is ignored).  Continue long
       lines by starting the next line with whitespace. Specify "!pattern" to exclude a name from
       the list. The form "!/file/name" is supported only in Postfix version 2.4 and later.

       Examples:

       masquerade_exceptions = root, mailer-daemon
       masquerade_exceptions = root

master_service_disable (default: empty)
       Selectively  disable master(8) listener ports by service type or by service name and type.
       Specify a list of service types ("inet", "unix", "fifo", or "pass") or "name.type" tuples,
       where "name" is the first field of a master.cf entry and "type" is a service type. As with
       other Postfix matchlists, a search stops  at  the  first  match.   Specify  "!pattern"  to
       exclude a service from the list. By default, all master(8) listener ports are enabled.

       Note:  this  feature  does  not support "/file/name" or "type:table" patterns, nor does it
       support wildcards such as "*" or "all". This is intentional.

       Examples:

       # Turn on all master(8) listener ports (the default).
       master_service_disable =
       # Turn off only the main SMTP listener port.
       master_service_disable = smtp.inet
       # Turn off all TCP/IP listener ports.
       master_service_disable = inet
       # Turn off all TCP/IP listener ports except "foo".
       master_service_disable = !foo.inet, inet

       This feature is available in Postfix 2.6 and later.

max_idle (default: 100s)
       The maximum amount of time that an idle Postfix daemon process waits for an incoming  con-
       nection	before	terminating  voluntarily.  This parameter is ignored by the Postfix queue
       manager and by other long-lived Postfix daemon processes.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

max_use (default: 100)
       The  maximal  number  of  incoming  connections that a Postfix daemon process will service
       before terminating voluntarily.	This parameter is ignored by the  Postfix  queue  manager
       and by other long-lived Postfix daemon processes.

maximal_backoff_time (default: 4000s)
       The maximal time between attempts to deliver a deferred message.

       This  parameter	should	be set to a value greater than or equal to $minimal_backoff_time.
       See also $queue_run_delay.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

maximal_queue_lifetime (default: 5d)
       The maximal time a message is queued before it is sent back as undeliverable.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is d (days).

       Specify 0 when mail delivery should be tried only once.

message_reject_characters (default: empty)
       The set of characters that Postfix will reject  in  message  content.   The  usual  C-like
       escape  sequences are recognized: \a \b \f \n \r \t \v \ddd (up to three octal digits) and
       \\.

       Example:

       message_reject_characters = \0

       This feature is available in Postfix 2.3 and later.

message_size_limit (default: 10240000)
       The maximal size in bytes of a message, including envelope information.

       Note: be careful when making changes.  Excessively small values will result in the loss of
       non-delivery  notifications,  when a bounce message size exceeds the local or remote MTA's
       message size limit.

message_strip_characters (default: empty)
       The set of characters that Postfix will remove from message  content.   The  usual  C-like
       escape  sequences are recognized: \a \b \f \n \r \t \v \ddd (up to three octal digits) and
       \\.

       Example:

       message_strip_characters = \0

       This feature is available in Postfix 2.3 and later.

milter_command_timeout (default: 30s)
       The time limit for sending an SMTP command to a Milter (mail filter) application, and  for
       receiving the response.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).

       Time units: s (seconds), m (minutes), h (hours), d (days), w  (weeks).  The  default  time
       unit is s (seconds).

       This feature is available in Postfix 2.3 and later.

milter_connect_macros (default: see postconf -d output)
       The  macros that are sent to Milter (mail filter) applications after completion of an SMTP
       connection. See MILTER_README for a list of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_connect_timeout (default: 30s)
       The time limit for connecting to a Milter (mail filter) application, and  for  negotiating
       protocol options.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).

       Time units: s (seconds), m (minutes), h (hours), d (days), w  (weeks).  The  default  time
       unit is s (seconds).

       This feature is available in Postfix 2.3 and later.

milter_content_timeout (default: 300s)
       The  time limit for sending message content to a Milter (mail filter) application, and for
       receiving the response.

       Specify a non-zero time value (an integral value plus an optional one-letter  suffix  that
       specifies the time unit).

       Time  units:  s	(seconds),  m (minutes), h (hours), d (days), w (weeks). The default time
       unit is s (seconds).

       This feature is available in Postfix 2.3 and later.

milter_data_macros (default: see postconf -d output)
       The macros that are sent to version 4 or higher Milter (mail  filter)  applications  after
       the  SMTP  DATA	command.  See MILTER_README for a list of available macro names and their
       meanings.

       This feature is available in Postfix 2.3 and later.

milter_default_action (default: tempfail)
       The default action when a Milter (mail filter) application is unavailable  or  mis-config-
       ured. Specify one of the following:

       accept Proceed as if the mail filter was not present.

       reject Reject all further commands in this session with a permanent status code.

       tempfail
	      Reject all further commands in this session with a temporary status code.

       quarantine
	      Like  "accept",  but freeze the message in the "hold" queue. Available with Postfix
	      2.6 and later.

       This feature is available in Postfix 2.3 and later.

milter_end_of_data_macros (default: see postconf -d output)
       The macros that are sent to Milter (mail filter) applications after  the  message  end-of-
       data. See MILTER_README for a list of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_end_of_header_macros (default: see postconf -d output)
       The macros that are sent to Milter (mail filter) applications after the end of the message
       header. See MILTER_README for a list of available macro names and their meanings.

       This feature is available in Postfix 2.5 and later.

milter_header_checks (default: empty)
       Optional lookup tables for content inspection of message headers that are produced by Mil-
       ter  applications.   See  the  header_checks(5)	manual page available actions. Currently,
       PREPEND is not implemented.

       The following example sends all mail that is marked as SPAM to a  spam  handling  machine.
       Note that matches are case-insensitive by default.

       /etc/postfix/main.cf:
	   milter_header_checks = pcre:/etc/postfix/milter_header_checks

       /etc/postfix/milter_header_checks:
	   /^X-SPAM-FLAG:\s+YES/ FILTER mysmtp:sanitizer.example.com:25

       The  milter_header_checks  mechanism  could  also be used for whitelisting. For example it
       could be used to skip heavy content inspection for DKIM-signed mail  from  known  friendly
       domains.

       This feature is available in Postfix 2.7, and as an optional patch for Postfix 2.6.

milter_helo_macros (default: see postconf -d output)
       The  macros that are sent to Milter (mail filter) applications after the SMTP HELO or EHLO
       command. See MILTER_README for a list of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_macro_daemon_name (default: $myhostname)
       The {daemon_name} macro value for Milter (mail filter)  applications.   See  MILTER_README
       for a list of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_macro_v (default: $mail_name $mail_version)
       The  {v}  macro value for Milter (mail filter) applications.  See MILTER_README for a list
       of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_mail_macros (default: see postconf -d output)
       The macros that are sent to Milter (mail filter) applications after  the  SMTP  MAIL  FROM
       command. See MILTER_README for a list of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_protocol (default: 6)
       The mail filter protocol version and optional protocol extensions for communication with a
       Milter application; prior to Postfix 2.6 the default protocol is  2.  Postfix  sends  this
       version	number during the initial protocol handshake.  It should match the version number
       that is expected by the mail filter application (or by its Milter library).

       Protocol versions:

       2      Use Sendmail 8 mail filter protocol version 2 (default with Sendmail  version  8.11
	      .. 8.13 and Postfix version 2.3 ..  2.5).

       3      Use Sendmail 8 mail filter protocol version 3.

       4      Use Sendmail 8 mail filter protocol version 4.

       6      Use  Sendmail  8 mail filter protocol version 6 (default with Sendmail version 8.14
	      and Postfix version 2.6).

       Protocol extensions:

       no_header_reply
	      Specify this when the Milter application will not reply for each individual message
	      header.

       This feature is available in Postfix 2.3 and later.

milter_rcpt_macros (default: see postconf -d output)
       The  macros that are sent to Milter (mail filter) applications after the SMTP RCPT TO com-
       mand. See MILTER_README for a list of available macro names and their meanings.

       This feature is available in Postfix 2.3 and later.

milter_unknown_command_macros (default: see postconf -d output)
       The macros that are sent to version 3 or higher Milter (mail filter) applications after an
       unknown	SMTP  command.	 See  MILTER_README for a list of available macro names and their
       meanings.

       This feature is available in Postfix 2.3 and later.

mime_boundary_length_limit (default: 2048)
       The maximal length of MIME multipart boundary strings. The MIME	processor  is  unable  to
       distinguish  between  boundary  strings	that  do  not  differ  in  the first $mime_bound-
       ary_length_limit characters.

       This feature is available in Postfix 2.0 and later.

mime_header_checks (default: $header_checks)
       Optional lookup tables  for  content  inspection  of  MIME  related  message  headers,  as
       described in the header_checks(5) manual page.

       This feature is available in Postfix 2.0 and later.

mime_nesting_limit (default: 100)
       The  maximal  recursion	level  that the MIME processor will handle.  Postfix refuses mail
       that is nested deeper than the specified limit.

       This feature is available in Postfix 2.0 and later.

minimal_backoff_time (default: 300s)
       The minimal time between attempts to deliver a deferred message; prior to Postfix 2.4  the
       default value was 1000s.

       This  parameter also limits the time an unreachable destination is kept in the short-term,
       in-memory, destination status cache.

       This parameter should be set greater than or equal to $queue_run_delay.	See  also  $maxi-
       mal_backoff_time.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

multi_instance_directories (default: empty)
       An optional list of  non-default  Postfix  configuration  directories;  these  directories
       belong  to  additional Postfix instances that share the Postfix executable files and docu-
       mentation with the default Postfix instance, and that are started, stopped, etc., together
       with  the  default  Postfix  instance.	Specify a list of pathnames separated by comma or
       whitespace.

       When $multi_instance_directories is empty, the postfix(1) command runs in  single-instance
       mode  and  operates  on	a single Postfix instance only. Otherwise, the postfix(1) command
       runs in multi-instance mode and invokes the  multi-instance  manager  specified	with  the
       multi_instance_wrapper  parameter.  The multi-instance manager in turn executes postfix(1)
       commands for the default instance and for all Postfix instances in  $multi_instance_direc-
       tories.

       Currently, this parameter setting is ignored except for the default main.cf file.

       This feature is available in Postfix 2.6 and later.

multi_instance_enable (default: no)
       Allow this Postfix instance to be started, stopped, etc., by a multi-instance manager.  By
       default, new instances are created in a safe state that prevents them from  being  started
       inadvertently.  This parameter is reserved for the multi-instance manager.

       This feature is available in Postfix 2.6 and later.

multi_instance_group (default: empty)
       The  optional  instance	group  name of this Postfix instance. A group identifies closely-
       related Postfix instances that the multi-instance manager can  start,  stop,  etc.,  as	a
       unit.  This parameter is reserved for the multi-instance manager.

       This feature is available in Postfix 2.6 and later.

multi_instance_name (default: empty)
       The  optional  instance	name of this Postfix instance. This name becomes also the default
       value for the syslog_name parameter.

       This feature is available in Postfix 2.6 and later.

multi_instance_wrapper (default: empty)
       The pathname of a multi-instance manager command that the postfix(1) command invokes  when
       the  multi_instance_directories parameter value is non-empty. The pathname may be followed
       by initial command arguments separated by whitespace; shell metacharacters such as  quotes
       are not supported in this context.

       The  postfix(1) command invokes the manager command with the postfix(1) non-option command
       arguments on the manager command line, and with all installation configuration  parameters
       exported into the manager command process environment. The manager command in turn invokes
       the postfix(1) command for individual Postfix instances as  "postfix  -c  config_directory
       command".

       This feature is available in Postfix 2.6 and later.

multi_recipient_bounce_reject_code (default: 550)
       The  numerical  Postfix	SMTP  server  response	code when a remote SMTP client request is
       blocked by the reject_multi_recipient_bounce restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

       This feature is available in Postfix 2.1 and later.

mydestination (default: $myhostname, localhost.$mydomain, localhost)
       The list of domains that are delivered via the $local_transport mail  delivery  transport.
       By  default  this  is the Postfix local(8) delivery agent which looks up all recipients in
       /etc/passwd  and  /etc/aliases.	The  SMTP  server  validates  recipient  addresses   with
       $local_recipient_maps and rejects non-existent recipients. See also the local domain class
       in the ADDRESS_CLASS_README file.

       The default mydestination value specifies names for the local machine  only.   On  a  mail
       domain gateway, you should also include $mydomain.

       The   $local_transport	delivery   method   is	 also  selected  for  mail  addressed  to
       user@[the.net.work.address] of the mail	system	(the  IP  addresses  specified	with  the
       inet_interfaces and proxy_interfaces parameters).

       Warnings:

       o      Do  not  specify	the  names of virtual domains - those domains are specified else-
	      where. See VIRTUAL_README for more information.

       o      Do not specify the names of domains that this machine is backup MX  host	for.  See
	      STANDARD_CONFIGURATION_README for how to set up backup MX hosts.

       o      By default, the Postfix SMTP server rejects mail for recipients not listed with the
	      local_recipient_maps parameter.  See the postconf(5) manual for  a  description  of
	      the local_recipient_maps and unknown_local_recipient_reject_code parameters.

       Specify	a  list of host or domain names, "/file/name" or "type:table" patterns, separated
       by commas and/or whitespace. A  "/file/name"  pattern  is  replaced  by	its  contents;	a
       "type:table"  lookup  table is matched when a name matches a lookup key (the lookup result
       is ignored).  Continue long lines by starting the next line with whitespace.

       Examples:

       mydestination = $myhostname, localhost.$mydomain $mydomain
       mydestination = $myhostname, localhost.$mydomain www.$mydomain, ftp.$mydomain

mydomain (default: see postconf -d output)
       The internet domain name of this mail system.  The default is to use $myhostname minus the
       first component, or "localdomain" (Postfix 2.3 and later).  $mydomain is used as a default
       value for many other configuration parameters.

       Example:

       mydomain = domain.tld

myhostname (default: see postconf -d output)
       The internet hostname of this mail system. The  default	is  to	use  the  fully-qualified
       domain  name  (FQDN)  from gethostname(), or to use the non-FQDN result from gethostname()
       and append ".$mydomain".  $myhostname is used as a default value for many other configura-
       tion parameters.

       Example:

       myhostname = host.example.com

mynetworks (default: see postconf -d output)
       The list of "trusted" SMTP clients that have more privileges than "strangers".

       In  particular, "trusted" SMTP clients are allowed to relay mail through Postfix.  See the
       smtpd_recipient_restrictions parameter description in the postconf(5) manual.

       You can specify the list of "trusted" network addresses by hand or you can let Postfix  do
       it  for you (which is the default).  See the description of the mynetworks_style parameter
       for more information.

       If you specify the mynetworks list by hand, Postfix ignores the mynetworks_style setting.

       Specify a list of network addresses  or	network/netmask  patterns,  separated  by  commas
       and/or whitespace. Continue long lines by starting the next line with whitespace.

       The  netmask  specifies the number of bits in the network part of a host address.  You can
       also specify "/file/name" or "type:table" patterns.  A "/file/name" pattern is replaced by
       its  contents;  a "type:table" lookup table is matched when a table entry matches a lookup
       string (the lookup result is ignored).

       The list is matched left to right, and the search  stops  on  the  first  match.   Specify
       "!pattern" to exclude an address or network block from the list. The form "!/file/name" is
       supported only in Postfix version 2.4 and later.

       Note: IP version 6 address information must be  specified  inside  []  in  the  mynetworks
       value,  and  in files specified with "/file/name".  IP version 6 addresses contain the ":"
       character, and would otherwise be confused with a "type:table" pattern.

       Examples:

       mynetworks = 127.0.0.0/8 168.100.189.0/28
       mynetworks = !192.168.0.1, 192.168.0.0/28
       mynetworks = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [2001:240:587::]/64
       mynetworks = $config_directory/mynetworks
       mynetworks = hash:/etc/postfix/network_table

mynetworks_style (default: subnet)
       The method to generate the default value for the mynetworks parameter.  This is	the  list
       of trusted networks for relay access control etc.

       o      Specify  "mynetworks_style  =  host"  when  Postfix  should  "trust" only the local
	      machine.

       o      Specify "mynetworks_style = subnet" when Postfix should "trust" SMTP clients in the
	      same IP subnetworks as the local machine.  On Linux, this works correctly only with
	      interfaces specified with the "ifconfig" command.

       o      Specify "mynetworks_style = class" when Postfix should "trust" SMTP clients in  the
	      same  IP	class  A/B/C  networks as the local machine.  Don't do this with a dialup
	      site - it would cause Postfix to "trust" your entire provider's network.	 Instead,
	      specify  an explicit mynetworks list by hand, as described with the mynetworks con-
	      figuration parameter.

myorigin (default: $myhostname)
       The domain name that locally-posted mail appears to come from,  and  that  locally  posted
       mail is delivered to. The default, $myhostname, is adequate for small sites.  If you run a
       domain with multiple machines, you should (1) change this to $mydomain and (2)  set  up	a
       domain-wide alias database that aliases each user to user@that.users.mailhost.

       Example:

       myorigin = $mydomain

nested_header_checks (default: $header_checks)
       Optional lookup tables for content inspection of non-MIME message headers in attached mes-
       sages, as described in the header_checks(5) manual page.

       This feature is available in Postfix 2.0 and later.

newaliases_path (default: see postconf -d output)
       Sendmail compatibility feature that specifies the location of the  newaliases(1)  command.
       This command can be used to rebuild the local(8) aliases(5) database.

non_fqdn_reject_code (default: 504)
       The  numerical  Postfix	SMTP  server  reply code when a client request is rejected by the
       reject_non_fqdn_helo_hostname,	reject_non_fqdn_sender	  or	reject_non_fqdn_recipient
       restriction.

non_smtpd_milters (default: empty)
       A  list	of  Milter  (mail  filter) applications for new mail that does not arrive via the
       Postfix smtpd(8) server. This includes local submission via the sendmail(1) command  line,
       new  mail  that	arrives via the Postfix qmqpd(8) server, and old mail that is re-injected
       into the queue with "postsuper -r".  See the MILTER_README document for details.

       This feature is available in Postfix 2.3 and later.

notify_classes (default: resource, software)
       The list of error classes that are reported to the postmaster. The default  is  to  report
       only  the most serious problems. The paranoid may wish to turn on the policy (UCE and mail
       relaying) and protocol error (broken mail software) reports.

       NOTE: postmaster notifications may contain confidential information such as SASL passwords
       or  message content.  It is the system administrator's responsibility to treat such infor-
       mation with care.

       The error classes are:

       bounce (also implies 2bounce)
	      Send the postmaster copies of the headers of bounced mail, and send transcripts  of
	      SMTP  sessions  when  Postfix rejects mail. The notification is sent to the address
	      specified with the bounce_notice_recipient configuration parameter (default:  post-
	      master).

       2bounce
	      Send  undeliverable bounced mail to the postmaster. The notification is sent to the
	      address  specified  with	the  2bounce_notice_recipient	configuration	parameter
	      (default: postmaster).

       delay  Send the postmaster copies of the headers of delayed mail. The notification is sent
	      to the address specified with the  delay_notice_recipient  configuration	parameter
	      (default: postmaster).

       policy Send  the  postmaster  a	transcript  of the SMTP session when a client request was
	      rejected because of (UCE) policy. The notification is sent to the address specified
	      with the error_notice_recipient configuration parameter (default: postmaster).

       protocol
	      Send  the  postmaster  a transcript of the SMTP session in case of client or server
	      protocol errors. The notification  is  sent  to  the  address  specified	with  the
	      error_notice_recipient configuration parameter (default: postmaster).

       resource
	      Inform  the postmaster of mail not delivered due to resource problems.  The notifi-
	      cation is sent to the address specified with the error_notice_recipient  configura-
	      tion parameter (default: postmaster).

       software
	      Inform  the postmaster of mail not delivered due to software problems.  The notifi-
	      cation is sent to the address specified with the error_notice_recipient  configura-
	      tion parameter (default: postmaster).

       Examples:

       notify_classes = bounce, delay, policy, protocol, resource, software
       notify_classes = 2bounce, resource, software

owner_request_special (default: yes)
       Give  special  treatment  to owner-listname and listname-request address localparts: don't
       split such addresses when the recipient_delimiter is set to "-".  This feature  is  useful
       for mailing lists.

parent_domain_matches_subdomains (default: see postconf -d output)
       What Postfix features match subdomains of "domain.tld" automatically, instead of requiring
       an explicit ".domain.tld" pattern.  This is planned backwards compatibility:   eventually,
       all  Postfix  features  are expected to require explicit ".domain.tld" style patterns when
       you really want to match subdomains.

permit_mx_backup_networks (default: empty)
       Restrict the use of the permit_mx_backup SMTP access feature to only domains whose primary
       MX  hosts  match  the listed networks.  The parameter value syntax is the same as with the
       mynetworks parameter; note, however, that the default value is empty.

pickup_service_name (default: pickup)
       The name of the pickup(8) service. This service picks up local mail submissions	from  the
       Postfix maildrop queue.

       This feature is available in Postfix 2.0 and later.

plaintext_reject_code (default: 450)
       The  numerical  Postfix	SMTP  server  response	code  when  a  request is rejected by the
       reject_plaintext_session restriction.

       This feature is available in Postfix 2.3 and later.

postmulti_control_commands (default: reload flush)
       The postfix(1) commands that the postmulti(1) instance manager treats  as  "control"  com-
       mands,  that  operate  on  running  instances.  For these commands, disabled instances are
       skipped.

       This feature is available in Postfix 2.6 and later.

postmulti_start_commands (default: start)
       The postfix(1) commands that the postmulti(1) instance manager treats as "start" commands.
       For these commands, disabled instances are "checked" rather than "started", and failure to
       "start" a member instance of an instance group will abort the start-up of later instances.

       This feature is available in Postfix 2.6 and later.

postmulti_stop_commands (default: see postconf -d output)
       The postfix(1) commands that the postmulti(1) instance manager treats as "stop"	commands.
       For these commands, disabled instances are skipped, and enabled instances are processed in
       reverse order.

       This feature is available in Postfix 2.6 and later.

postscreen_access_list (default: permit_mynetworks)
       Permanent white/blacklist for remote SMTP client  IP  addresses.   postscreen(8)  searches
       this  list  immediately	after  a remote SMTP client connects.  Specify a comma- or white-
       space-separated list of commands (in upper or lower case) or  lookup  tables.  The  search
       stops upon the first command that fires for the client IP address.

	permit_mynetworks
	      Whitelist  the  client  and  terminate  the search if the client IP address matches
	      $mynetworks.  Do not subject the client to any  before/after  220  greeting  tests.
	      Pass the connection immediately to a Postfix SMTP server process.

	type:table
	      Query  the  specified  lookup  table.  Each  table lookup result is an access list,
	      except that access lists inside a table cannot specify type:table entries.
	      To discourage the use of hash, btree, etc. tables, there is  no  support	for  sub-
	      string matching like smtpd(8). Use CIDR tables instead.

	permit
	      Whitelist  the  client  and  terminate the search. Do not subject the client to any
	      before/after 220 greeting tests. Pass the connection immediately to a Postfix  SMTP
	      server process.

	reject
	      Blacklist  the  client  and  terminate the search. Subject the client to the action
	      configured with the postscreen_blacklist_action configuration parameter.

	dunno All postscreen(8) access lists implicitly have this command at the end.
	      When  dunno is executed inside a lookup table, return from  the  lookup  table  and
	      evaluate the next command.
	      When   dunno  is executed outside a lookup table, terminate the search, and subject
	      the client to the configured before/after 220 greeting tests.

       Example:

       /etc/postfix/main.cf:
	   postscreen_access_list = permit_mynetworks,
		 cidr:/etc/postfix/postscreen_access.cidr

       /etc/postfix/postscreen_access.cidr:
	   # Rules are evaluated in the order as specified.
	   # Blacklist 192.168.* except 192.168.0.1.
	   192.168.0.1	       dunno
	   192.168.0.0/16      reject

       This feature is available in Postfix 2.8.

postscreen_bare_newline_action (default: ignore)
       The action that postscreen(8) takes when an SMTP client sends a	bare  newline  character,
       that is, a newline not preceded by carriage return.  Specify one of the following:

       ignore Ignore the failure of this test. Allow other tests to complete.  Do not repeat this
	      test before some the result from some other test expires.  This  option  is  useful
	      for testing and collecting statistics without blocking mail permanently.

       enforce
	      Allow  other  tests  to  complete.  Reject attempts to deliver mail with a 550 SMTP
	      reply, and log the helo/sender/recipient information.  Repeat this  test	the  next
	      time the client connects.

       drop   Drop  the  connection  immediately with a 521 SMTP reply. Repeat this test the next
	      time the client connects.

       This feature is available in Postfix 2.8.

postscreen_bare_newline_enable (default: no)
       Enable "bare newline" SMTP protocol tests in the postscreen(8)  server.	These  tests  are
       expensive: a client must disconnect after it passes the test, before it can talk to a real
       Postfix SMTP server.

       This feature is available in Postfix 2.8.

postscreen_bare_newline_ttl (default: 30d)
       The amount of time that postscreen(8) will use the result from a successful "bare newline"
       SMTP  protocol  test.  During this time, the client IP address is excluded from this test.
       The default is long because a client must disconnect after it passes the test,  before  it
       can talk to a real Postfix SMTP server.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).  Time units: s (seconds), m (minutes), h (hours),  d  (days),	w
       (weeks).

       This feature is available in Postfix 2.8.

postscreen_blacklist_action (default: ignore)
       The  action  that  postscreen(8) takes when an SMTP client is permanently blacklisted with
       the postscreen_access_list parameter.  Specify one of the following:

       ignore (default)
	      Ignore  this result. Allow other tests to complete.  Repeat this test the next time
	      the  client  connects.  This option is useful for testing and collecting statistics
	      without blocking mail.

       enforce
	      Allow other tests to complete. Reject attempts to deliver  mail  with  a	550  SMTP
	      reply,  and  log	the helo/sender/recipient information.	Repeat this test the next
	      time the client connects.

       drop   Drop the connection immediately with a 521 SMTP reply. Repeat this  test	the  next
	      time the client connects.

       This feature is available in Postfix 2.8.

postscreen_cache_cleanup_interval (default: 12h)
       The  amount of time between postscreen(8) cache cleanup runs.  Cache cleanup increases the
       load on the cache database and should  therefore  not  be  run  frequently.  This  feature
       requires  that the cache database supports the "delete" and "sequence" operators.  Specify
       a zero interval to disable cache cleanup.

       After each cache cleanup run, the postscreen(8) daemon logs the	number	of  entries  that
       were retained and dropped. A cleanup run is logged as "partial" when the daemon terminates
       early after "postfix reload", "postfix stop", or no requests for $max_idle seconds.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_cache_map (default: btree:$data_directory/postscreen_cache)
       Persistent storage for the postscreen(8) server decisions.

       This feature is available in Postfix 2.8.

postscreen_cache_retention_time (default: 7d)
       The amount of time that postscreen(8) will cache  an  expired  temporary  whitelist  entry
       before  it is removed. This prevents clients from being logged as "NEW" just because their
       cache entry expired an hour ago. It also prevents the cache from filling up  with  clients
       that passed some deep protocol test once and never came back.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_client_connection_count_limit (default: $smtpd_client_connection_count_limit)
       How  many  simultaneous	connections  any client is allowed to have with the postscreen(8)
       daemon. By default, this limit is the same as with the Postfix SMTP server. Note that  the
       triage  process	can  take  several  seconds, with the time spent in postscreen_greet_wait
       delay, and with the time spent talking to the postscreen(8) built-in dummy  SMTP  protocol
       engine.

       This feature is available in Postfix 2.8.

postscreen_command_count_limit (default: 20)
       The  limit  on  the total number of commands per SMTP session for postscreen(8)'s built-in
       SMTP protocol engine.  This SMTP engine defers or rejects all attempts  to  deliver  mail,
       therefore  there  is no need to enforce separate limits on the number of junk commands and
       error commands.

       This feature is available in Postfix 2.8.

postscreen_command_filter (default: $smtpd_command_filter)
       A mechanism to transform commands from remote SMTP clients.  See smtpd_command_filter  for
       further details.

       This feature is available in Postfix 2.8 and later.

postscreen_command_time_limit (default: ${stress?10}${stress:300}s)
       The  time limit to read an entire command line with postscreen(8)'s built-in SMTP protocol
       engine.

       This feature is available in Postfix 2.8.

postscreen_disable_vrfy_command (default: $disable_vrfy_command)
       Disable the SMTP VRFY command in the postscreen(8) daemon.  See	disable_vrfy_command  for
       details.

       This feature is available in Postfix 2.8.

postscreen_discard_ehlo_keyword_address_maps (default: $smtpd_discard_ehlo_keyword_address_maps)
       Lookup  tables,	indexed by the remote SMTP client address, with case insensitive lists of
       EHLO keywords (pipelining, starttls, auth, etc.) that the postscreen(8)	server	will  not
       send  in  the  EHLO  response to a remote SMTP client. See smtpd_discard_ehlo_keywords for
       details.  The table is not searched by hostname for robustness reasons.

       This feature is available in Postfix 2.8 and later.

postscreen_discard_ehlo_keywords (default: $smtpd_discard_ehlo_keywords)
       A case insensitive list of EHLO keywords  (pipelining,  starttls,  auth,  etc.)	that  the
       postscreen(8)  server  will  not  send  in  the EHLO response to a remote SMTP client. See
       smtpd_discard_ehlo_keywords for details.

       This feature is available in Postfix 2.8 and later.

postscreen_dnsbl_action (default: ignore)
       The action that postscreen(8) takes when an SMTP client's combined DNSBL score is equal to
       or   greater   than   a	 threshold   (as  defined  with  the  postscreen_dnsbl_sites  and
       postscreen_dnsbl_threshold parameters).	Specify one of the following:

       ignore (default)
	      Ignore the failure of this test. Allow other tests to complete.  Repeat  this  test
	      the  next time the client connects.  This option is useful for testing and collect-
	      ing statistics without blocking mail.

       enforce
	      Allow other tests to complete. Reject attempts to deliver  mail  with  a	550  SMTP
	      reply,  and  log	the helo/sender/recipient information.	Repeat this test the next
	      time the client connects.

       drop   Drop the connection immediately with a 521 SMTP reply. Repeat this  test	the  next
	      time the client connects.

       This feature is available in Postfix 2.8.

postscreen_dnsbl_reply_map (default: empty)
       A  mapping  from  actual  DNSBL domain name which includes a secret password, to the DNSBL
       domain name that postscreen will reply with when it rejects  mail.   When  no  mapping  is
       found, the actual DNSBL domain will be used.

       For  maximal  stability	it  is best to use a file that is read into memory such as pcre:,
       regexp: or texthash: (texthash: is similar to hash:, except a) there is	no  need  to  run
       postmap(1) before the file can be used, and b) texthash: does not detect changes after the
       file is read).

       Example:

       /etc/postfix/main.cf:
	   postscreen_dnsbl_reply_map = texthash:/etc/postfix/dnsbl_reply

       /etc/postfix/dnsbl_reply:
	  secret.zen.spamhaus.org    zen.spamhaus.org

       This feature is available in Postfix 2.8.

postscreen_dnsbl_sites (default: empty)
       Optional list of DNS white/blacklist domains, filters and weight factors. When the list is
       non-empty,  the dnsblog(8) daemon will query these domains with the IP addresses of remote
       SMTP clients, and postscreen(8) will update an SMTP client's DNSBL score  with  each  non-
       error reply.

       Caution:  when  postscreen  rejects  mail,  it replies with the DNSBL domain name. Use the
       postscreen_dnsbl_reply_map feature to hide "password" information in DNSBL domain names.

       When a  client's  score	is  equal  to  or  greater  than  the  threshold  specified  with
       postscreen_dnsbl_threshold, postscreen(8) can drop the connection with the SMTP client.

       Specify a list of domain=filter*weight entries, separated by comma or whitespace.

       o      When  no	"=filter" is specified, postscreen(8) will use any non-error DNSBL reply.
	      Otherwise, postscreen(8) uses only DNSBL replies that match the filter. The  filter
	      has  the	form  d.d.d.d, where each d is a number, or a pattern inside [] that con-
	      tains one or more ";"-separated numbers or number..number ranges.

       o      When no "*weight" is specified, postscreen(8) increments the  SMTP  client's  DNSBL
	      score  by  1.   Otherwise, the weight must be an integral number, and postscreen(8)
	      adds the specified weight to the SMTP client's DNSBL  score.   Specify  a  negative
	      number for whitelisting.

       o      When   one   postscreen_dnsbl_sites   entry   produces  multiple	DNSBL  responses,
	      postscreen(8) applies the weight at most once.

       Examples:

       To use example.com as a high-confidence blocklist, and to block mail with example.net  and
       example.org only when both agree:

       postscreen_dnsbl_threshold = 2
       postscreen_dnsbl_sites = example.com*2, example.net, example.org

       To filter only DNSBL replies containing 127.0.0.4:

       postscreen_dnsbl_sites = example.com=127.0.0.4

       This feature is available in Postfix 2.8.

postscreen_dnsbl_threshold (default: 1)
       The  inclusive  lower bound for blocking an SMTP client, based on its combined DNSBL score
       as defined with the postscreen_dnsbl_sites parameter.

       This feature is available in Postfix 2.8.

postscreen_dnsbl_ttl (default: 1h)
       The amount of time that postscreen(8) will use the result from a successful DNS	blocklist
       test.  During  this time, the client IP address is excluded from this test. The default is
       relatively short, because a good client can  immediately  talk  to  a  real  Postfix  SMTP
       server.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).  Time units: s (seconds), m (minutes), h (hours),  d  (days),	w
       (weeks).

       This feature is available in Postfix 2.8.

postscreen_enforce_tls (default: $smtpd_enforce_tls)
       Mandatory TLS: announce STARTTLS support to SMTP clients, and require that clients use TLS
       encryption.  See smtpd_postscreen_enforce_tls for details.

       This feature is available in Postfix 2.8 and later.  Preferably, use  postscreen_tls_secu-
       rity_level instead.

postscreen_expansion_filter (default: see postconf -d output)
       List  of  characters  that are permitted in postscreen_reject_footer attribute expansions.
       See smtpd_expansion_filter for further details.

       This feature is available in Postfix 2.8 and later.

postscreen_forbidden_commands (default: $smtpd_forbidden_commands)
       List of commands that the postscreen(8) server considers in violation of the  SMTP  proto-
       col.  See  smtpd_forbidden_commands for syntax, and postscreen_non_smtp_command_action for
       possible actions.

       This feature is available in Postfix 2.8.

postscreen_greet_action (default: ignore)
       The action that postscreen(8) takes when an SMTP client speaks before its turn within  the
       time specified with the postscreen_greet_wait parameter.  Specify one of the following:

       ignore (default)
	      Ignore  the  failure of this test. Allow other tests to complete.  Repeat this test
	      the next time the client connects.  This option is useful for testing and  collect-
	      ing statistics without blocking mail.

       enforce
	      Allow  other  tests  to  complete.  Reject attempts to deliver mail with a 550 SMTP
	      reply, and log the helo/sender/recipient information.  Repeat this  test	the  next
	      time the client connects.

       drop   Drop  the  connection  immediately with a 521 SMTP reply. Repeat this test the next
	      time the client connects.

       In either case, postscreen(8) will not whitelist the SMTP client IP address.

       This feature is available in Postfix 2.8.

postscreen_greet_banner (default: $smtpd_banner)
       The text in the optional "220-text..." server response that postscreen(8) sends	ahead  of
       the  real  Postfix SMTP server's "220 text..." response, in an attempt to confuse bad SMTP
       clients so that they speak before their turn (pre-greet).  Specify an empty value to  dis-
       able this feature.

       This feature is available in Postfix 2.8.

postscreen_greet_ttl (default: 1d)
       The amount of time that postscreen(8) will use the result from a successful PREGREET test.
       During this time, the client IP address is excluded from this test. The default	is  rela-
       tively short, because a good client can immediately talk to a real Postfix SMTP server.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).  Time units: s (seconds), m (minutes), h (hours),  d  (days),	w
       (weeks).

       This feature is available in Postfix 2.8.

postscreen_greet_wait (default: ${stress?2}${stress:6}s)
       The  amount  of	time  that  postscreen(8)  will wait for an SMTP client to send a command
       before its turn, and for DNS blocklist lookup results to arrive (default: up to 2  seconds
       under stress, up to 6 seconds otherwise).

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_helo_required (default: $smtpd_helo_required)
       Require that a remote SMTP client sends HELO or EHLO before commencing a MAIL transaction.

       This feature is available in Postfix 2.8.

postscreen_non_smtp_command_action (default: drop)
       The action that postscreen(8) takes when an SMTP client sends non-SMTP commands as  speci-
       fied with the postscreen_forbidden_commands parameter.  Specify one of the following:

       ignore Ignore the failure of this test. Allow other tests to complete.  Do not repeat this
	      test before some the result from some other test expires.  This  option  is  useful
	      for testing and collecting statistics without blocking mail permanently.

       enforce
	      Allow  other  tests  to  complete.  Reject attempts to deliver mail with a 550 SMTP
	      reply, and log the helo/sender/recipient information.  Repeat this  test	the  next
	      time the client connects.

       drop   Drop  the  connection  immediately with a 521 SMTP reply. Repeat this test the next
	      time the client connects. This action is the same as with the Postfix SMTP server's
	      smtpd_forbidden_commands feature.

       This feature is available in Postfix 2.8.

postscreen_non_smtp_command_enable (default: no)
       Enable  "non-SMTP command" tests in the postscreen(8) server. These tests are expensive: a
       client must disconnect after it passes the test, before it can talk to a real Postfix SMTP
       server.

       This feature is available in Postfix 2.8.

postscreen_non_smtp_command_ttl (default: 30d)
       The amount of time that postscreen(8) will use the result from a successful "non_smtp_com-
       mand" SMTP protocol test. During this time, the client IP address is  excluded  from  this
       test.  The  default  is	long  because  a client must disconnect after it passes the test,
       before it can talk to a real Postfix SMTP server.

       Specify a non-zero time value (an integral value plus an optional one-letter  suffix  that
       specifies  the  time  unit).  Time units: s (seconds), m (minutes), h (hours), d (days), w
       (weeks).

       This feature is available in Postfix 2.8.

postscreen_pipelining_action (default: enforce)
       The action that postscreen(8) takes when an SMTP client sends multiple commands instead of
       sending one command and waiting for the server to respond.  Specify one of the following:

       ignore Ignore the failure of this test. Allow other tests to complete.  Do not repeat this
	      test before some the result from some other test expires.  This  option  is  useful
	      for testing and collecting statistics without blocking mail permanently.

       enforce
	      Allow  other  tests  to  complete.  Reject attempts to deliver mail with a 550 SMTP
	      reply, and log the helo/sender/recipient information.  Repeat this  test	the  next
	      time the client connects.

       drop   Drop  the  connection  immediately with a 521 SMTP reply. Repeat this test the next
	      time the client connects.

       This feature is available in Postfix 2.8.

postscreen_pipelining_enable (default: no)
       Enable "pipelining" SMTP protocol tests in  the	postscreen(8)  server.	These  tests  are
       expensive: a good client must disconnect after it passes the test, before it can talk to a
       real Postfix SMTP server.

       This feature is available in Postfix 2.8.

postscreen_pipelining_ttl (default: 30d)
       The amount of time that postscreen(8) will use the result from a  successful  "pipelining"
       SMTP  protocol  test.  During this time, the client IP address is excluded from this test.
       The default is long because a good client must disconnect after it passes the test, before
       it can talk to a real Postfix SMTP server.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).  Time units: s (seconds), m (minutes), h (hours),  d  (days),	w
       (weeks).

       This feature is available in Postfix 2.8.

postscreen_post_queue_limit (default: $default_process_limit)
       The  number  of	clients  that can be waiting for service from a real SMTP server process.
       When this queue is full, all clients will receive a 421 reponse.

       This feature is available in Postfix 2.8.

postscreen_pre_queue_limit (default: $default_process_limit)
       The number of non-whitelisted clients that can be waiting for a decision whether they will
       receive	service  from  a  real	SMTP  server  process.	When this queue is full, all non-
       whitelisted clients will receive a 421 reponse.

       This feature is available in Postfix 2.8.

postscreen_reject_footer (default: $smtpd_reject_footer)
       Optional  information  that  is	appended  after  a  4XX  or  5XX  server  response.   See
       smtpd_reject_footer for further details.

       This feature is available in Postfix 2.8 and later.

postscreen_tls_security_level (default: $smtpd_tls_security_level)
       The SMTP TLS security level for the postscreen(8) server; when a non-empty value is speci-
       fied,	this	overrides    the    obsolete	parameters     postscreen_use_tls     and
       postscreen_enforce_tls. See smtpd_tls_security_level for details.

       This feature is available in Postfix 2.8 and later.

postscreen_use_tls (default: $smtpd_use_tls)
       Opportunistic  TLS:  announce  STARTTLS	support  to SMTP clients, but do not require that
       clients use TLS encryption.

       This feature is available in Postfix 2.8 and later.  Preferably, use  postscreen_tls_secu-
       rity_level instead.

postscreen_watchdog_timeout (default: 10s)
       How  much time a postscreen(8) process may take to respond to an SMTP client command or to
       perform a cache operation before it is terminated by a built-in watchdog timer.	This is a
       safety  mechanism that prevents postscreen(8) from becoming non-responsive due to a bug in
       Postfix itself or in system software.  To avoid false alarms and unnecessary cache corrup-
       tion this limit cannot be set under 10s.

       Specify	a  non-zero time value (an integral value plus an optional one-letter suffix that
       specifies the time unit).  Time units: s (seconds), m (minutes), h (hours),  d  (days),	w
       (weeks).

       This feature is available in Postfix 2.8.

prepend_delivered_header (default: command, file, forward)
       The  message delivery contexts where the Postfix local(8) delivery agent prepends a Deliv-
       ered-To:  message header with the address that the mail was delivered to. This information
       is used for mail delivery loop detection.

       By default, the Postfix local delivery agent prepends a Delivered-To: header when forward-
       ing mail and when delivering to file (mailbox) and command. Turning off the  Delivered-To:
       header when forwarding mail is not recommended.

       Specify zero or more of forward, file, or command.

       Example:

       prepend_delivered_header = forward

process_id (read-only)
       The process ID of a Postfix command or daemon process.

process_id_directory (default: pid)
       The  location  of  Postfix  PID	files  relative to $queue_directory.  This is a read-only
       parameter.

process_name (read-only)
       The process name of a Postfix command or daemon process.

propagate_unmatched_extensions (default: canonical, virtual)
       What address lookup tables copy an address extension from the lookup  key  to  the  lookup
       result.

       For  example,  with a virtual(5) mapping of "joe@example.com => joe.user@example.net", the
       address "joe+foo@example.com" would rewrite to "joe.user+foo@example.net".

       Specify zero or more of canonical, virtual, alias,  forward,  include  or  generic.  These
       cause  address  extension  propagation with canonical(5), virtual(5), and aliases(5) maps,
       with local(8) .forward and :include: file lookups, and with smtp(8) generic maps,  respec-
       tively.

       Note:  enabling this feature for types other than canonical and virtual is likely to cause
       problems when mail is forwarded to other sites, especially with mail that  is  sent  to	a
       mailing list exploder address.

       Examples:

       propagate_unmatched_extensions = canonical, virtual, alias,
	       forward, include
       propagate_unmatched_extensions = canonical, virtual

proxy_interfaces (default: empty)
       The  network  interface addresses that this mail system receives mail on by way of a proxy
       or network address translation unit.

       This feature is available in Postfix 2.0 and later.

       You must specify your "outside" proxy/NAT addresses when your system is a backup  MX  host
       for  other  domains, otherwise mail delivery loops will happen when the primary MX host is
       down.

       Example:

       proxy_interfaces = 1.2.3.4

proxy_read_maps (default: see postconf -d output)
       The lookup tables that the proxymap(8) server is allowed to access for the read-only  ser-
       vice.  Table references that don't begin with proxy: are ignored.

       This feature is available in Postfix 2.0 and later.

proxy_write_maps (default: see postconf -d output)
       The lookup tables that the proxymap(8) server is allowed to access for the read-write ser-
       vice. Postfix-owned  local  database  files  should  be	stored	under  the  Postfix-owned
       data_directory.	Table references that don't begin with proxy: are ignored.

       This feature is available in Postfix 2.5 and later.

proxymap_service_name (default: proxymap)
       The  name of the proxymap read-only table lookup service.  This service is normally imple-
       mented by the proxymap(8) daemon.

       This feature is available in Postfix 2.6 and later.

proxywrite_service_name (default: proxywrite)
       The name of the proxywrite read-write table lookup  service.   This  service  is  normally
       implemented by the proxymap(8) daemon.

       This feature is available in Postfix 2.6 and later.

qmgr_clog_warn_time (default: 300s)
       The  minimal delay between warnings that a specific destination is clogging up the Postfix
       active queue. Specify 0 to disable.

       This feature is enabled with the helpful_warnings parameter.

       This feature is available in Postfix 2.0 and later.

qmgr_daemon_timeout (default: 1000s)
       How much time a Postfix queue manager process may take to handle a request  before  it  is
       terminated by a built-in watchdog timer.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.8 and later.

qmgr_fudge_factor (default: 100)
       Obsolete feature: the percentage of delivery resources that a busy mail system will use up
       for delivery of a large mailing	list message.

       This  feature  exists  only  in	the oqmgr(8) old queue manager. The current queue manager
       solves the problem in a better way.

qmgr_ipc_timeout (default: 60s)
       The time limit for the queue manager to send or receive information over an internal  com-
       munication channel.  The purpose is to break out of deadlock situations. If the time limit
       is exceeded the software either retries or aborts the operation.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

       This feature is available in Postfix 2.8 and later.

qmgr_message_active_limit (default: 20000)
       The maximal number of messages in the active queue.

qmgr_message_recipient_limit (default: 20000)
       The maximal number of recipients held in memory by the Postfix queue manager, and the max-
       imal size of the size of the short-term, in-memory "dead" destination status cache.

qmgr_message_recipient_minimum (default: 10)
       The minimal number of in-memory recipients for any message. This takes priority	over  any
       other  in-memory  recipient  limits (i.e., the global qmgr_message_recipient_limit and the
       per transport _recipient_limit) if necessary. The minimum value allowed for this parameter
       is 1.

qmqpd_authorized_clients (default: empty)
       What clients are allowed to connect to the QMQP server port.

       By  default, no client is allowed to use the service. This is because the QMQP server will
       relay mail to any destination.

       Specify a list of client patterns. A list pattern specifies a host name, a domain name, an
       internet  address,  or a network/mask pattern, where the mask specifies the number of bits
       in the network part.  When a pattern specifies a file name, its contents  are  substituted
       for  the  file name; when a pattern is a "type:table" table specification, table lookup is
       used instead.

       Patterns are separated by whitespace and/or commas. In order to reverse the  result,  pre-
       cede  a pattern with an exclamation point (!). The form "!/file/name" is supported only in
       Postfix version 2.4 and later.

       Example:

       qmqpd_authorized_clients = !192.168.0.1, 192.168.0.0/24

qmqpd_client_port_logging (default: no)
       Enable logging of the remote QMQP client port in addition to the hostname and IP  address.
       The logging format is "host[address]:port".

       This feature is available in Postfix 2.5 and later.

qmqpd_error_delay (default: 1s)
       How  long  the  QMQP  server will pause before sending a negative reply to the client. The
       purpose is to slow down confused or malicious clients.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

qmqpd_timeout (default: 300s)
       The  time limit for sending or receiving information over the network.  If a read or write
       operation blocks for more than $qmqpd_timeout seconds the QMQP server gives up and discon-
       nects.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

queue_directory (default: see postconf -d output)
       The location of the Postfix top-level queue directory. This is the root directory of Post-
       fix daemon processes that run chrooted.

queue_file_attribute_count_limit (default: 100)
       The  maximal number of (name=value) attributes that may be stored in a Postfix queue file.
       The limit is enforced by the cleanup(8) server.

       This feature is available in Postfix 2.0 and later.

queue_minfree (default: 0)
       The minimal amount of free space in bytes in the queue  file  system  that  is  needed  to
       receive	mail.	This is currently used by the SMTP server to decide if it will accept any
       mail at all.

       By default, the Postfix SMTP server rejects MAIL FROM commands when  the  amount  of  free
       space  is less than 1.5*$message_size_limit (Postfix version 2.1 and later).  To specify a
       higher minimum free space limit, specify a queue_minfree value that is at least	1.5*$mes-
       sage_size_limit.

       With  Postfix  versions	2.0  and earlier, a queue_minfree value of zero means there is no
       minimum required amount of free space.

queue_run_delay (default: 300s)
       The time between deferred queue scans by the queue  manager;  prior  to	Postfix  2.4  the
       default value was 1000s.

       This  parameter should be set less than or equal to $minimal_backoff_time. See also $maxi-
       mal_backoff_time.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

queue_service_name (default: qmgr)
       The  name  of  the  qmgr(8)  service. This service manages the Postfix queue and schedules
       delivery requests.

       This feature is available in Postfix 2.0 and later.

rbl_reply_maps (default: empty)
       Optional lookup tables with RBL response templates. The tables  are  indexed  by  the  RBL
       domain  name.  By  default,  Postfix  uses  the	default  template  as  specified with the
       default_rbl_reply configuration parameter. See there for a discussion of the syntax of RBL
       reply templates.

       This feature is available in Postfix 2.0 and later.

readme_directory (default: see postconf -d output)
       The  location  of  Postfix README files that describe how to build, configure or operate a
       specific Postfix subsystem or feature.

receive_override_options (default: empty)
       Enable or disable recipient validation, built-in content filtering,  or	address  mapping.
       Typically,  these  are  specified in master.cf as command-line arguments for the smtpd(8),
       qmqpd(8) or pickup(8) daemons.

       Specify zero or more of the following options.  The options override main.cf settings  and
       are  either  implemented  by smtpd(8), qmqpd(8), or pickup(8) themselves, or they are for-
       warded to the cleanup server.

       no_unknown_recipient_checks
	      Do not try to reject unknown recipients (SMTP  server  only).   This  is	typically
	      specified AFTER an external content filter.

       no_address_mappings
	      Disable  canonical address mapping, virtual alias map expansion, address masquerad-
	      ing, and automatic BCC (blind carbon-copy) recipients. This is typically	specified
	      BEFORE an external content filter.

       no_header_body_checks
	      Disable  header/body_checks.  This is typically specified AFTER an external content
	      filter.

       no_milters
	      Disable Milter (mail filter) applications. This is  typically  specified	AFTER  an
	      external content filter.

       Note:  when  the  "BEFORE content filter" receive_override_options setting is specified in
       the main.cf file, specify the "AFTER content filter" receive_override_options  setting  in
       master.cf (and vice versa).

       Examples:

       receive_override_options =
	   no_unknown_recipient_checks, no_header_body_checks
       receive_override_options = no_address_mappings

       This feature is available in Postfix 2.1 and later.

recipient_bcc_maps (default: empty)
       Optional BCC (blind carbon-copy) address lookup tables, indexed by recipient address.  The
       BCC address (multiple results are not supported) is added when mail enters from outside of
       Postfix.

       This feature is available in Postfix 2.1 and later.

       The table search order is as follows:

       o      Look  up	the  "user+extension@domain.tld"  address  including the optional address
	      extension.

       o      Look up the "user@domain.tld" address without the optional address extension.

       o      Look up the "user+extension" address local part when the	recipient  domain  equals
	      $myorigin, $mydestination, $inet_interfaces or $proxy_interfaces.

       o      Look  up	the "user" address local part when the recipient domain equals $myorigin,
	      $mydestination, $inet_interfaces or $proxy_interfaces.

       o      Look up the "@domain.tld" part.

       Specify the types and names of databases to use.  After change,	run  "postmap  /etc/post-
       fix/recipient_bcc".

       Note: if mail to the BCC address bounces it will be returned to the sender.

       Note:  automatic  BCC  recipients  are produced only for new mail.  To avoid mailer loops,
       automatic BCC recipients are not generated after  Postfix  forwards  mail  internally,  or
       after Postfix generates mail itself.

       Example:

       recipient_bcc_maps = hash:/etc/postfix/recipient_bcc

recipient_canonical_classes (default: envelope_recipient, header_recipient)
       What  addresses	are  subject  to  recipient_canonical_maps  address mapping.  By default,
       recipient_canonical_maps address mapping is applied to envelope recipient  addresses,  and
       to header recipient addresses.

       Specify one or more of: envelope_recipient, header_recipient

       This feature is available in Postfix 2.2 and later.

recipient_canonical_maps (default: empty)
       Optional  address  mapping lookup tables for envelope and header recipient addresses.  The
       table format and lookups are documented in canonical(5).

       Note: $recipient_canonical_maps is processed before $canonical_maps.

       Example:

       recipient_canonical_maps = hash:/etc/postfix/recipient_canonical

recipient_delimiter (default: empty)
       The separator between user names and address  extensions  (user+foo).   See  canonical(5),
       local(8), relocated(5) and virtual(5) for the effects this has on aliases, canonical, vir-
       tual, relocated and on .forward file lookups.  Basically, the software tries user+foo  and
       .forward+foo before trying user and .forward.

       Example:

       recipient_delimiter = +

reject_code (default: 554)
       The  numerical  Postfix	SMTP  server  response	code when a remote SMTP client request is
       rejected by the "reject" restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

reject_tempfail_action (default: defer_if_permit)
       The Postfix SMTP server's action when a reject-type restriction fails due to  a	temporary
       error condition. Specify "defer" to defer the remote SMTP client request immediately. With
       the default "defer_if_permit" action, the Postfix SMTP server continues to look for oppor-
       tunities  to  reject  mail,  and  defers  the client request only if it would otherwise be
       accepted.

       For  finer  control,  see:  unverified_recipient_tempfail_action,  unverified_sender_temp-
       fail_action, unknown_address_tempfail_action, and unknown_helo_hostname_tempfail_action.

       This feature is available in Postfix 2.6 and later.

relay_clientcerts (default: empty)
       List of tables with remote SMTP client-certificate fingerprints for which the Postfix SMTP
       server will allow access with the permit_tls_clientcerts feature.  The fingerprint  digest
       algorithm  is  configurable  via the smtpd_tls_fingerprint_digest parameter (hard-coded as
       md5 prior to Postfix version 2.5).

       Postfix lookup tables are in the form of (key, value) pairs.  Since we only need the  key,
       the   value   can   be	chosen	 freely,   e.g.    the	 name	of   the  user	or  host:
       D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80 lutzpc.at.home

       Example:

       relay_clientcerts = hash:/etc/postfix/relay_clientcerts

       For more fine-grained control, use check_ccert_access to select an  appropriate	access(5)
       policy for each client.	See RESTRICTION_CLASS_README.

       This feature is available with Postfix version 2.2.

relay_destination_concurrency_limit (default: $default_destination_concurrency_limit)
       The  maximal  number  of parallel deliveries to the same destination via the relay message
       delivery transport. This limit is enforced by the  queue  manager.  The	message  delivery
       transport name is the first field in the entry in the master.cf file.

       This feature is available in Postfix 2.0 and later.

relay_destination_recipient_limit (default: $default_destination_recipient_limit)
       The  maximal  number  of  recipients per message for the relay message delivery transport.
       This limit is enforced by the queue manager. The message delivery transport  name  is  the
       first field in the entry in the master.cf file.

       Setting	this  parameter  to a value of 1 changes the meaning of relay_destination_concur-
       rency_limit from concurrency per domain into concurrency per recipient.

       This feature is available in Postfix 2.0 and later.

relay_domains (default: $mydestination)
       What destination domains (and subdomains thereof) this system will relay mail  to.  Subdo-
       main  matching  is  controlled  with  the  parent_domain_matches_subdomains parameter. For
       details about how the relay_domains value  is  used,  see  the  description  of	the  per-
       mit_auth_destination and reject_unauth_destination SMTP recipient restrictions.

       Domains	that  match  $relay_domains are delivered with the $relay_transport mail delivery
       transport. The SMTP server validates recipient addresses  with  $relay_recipient_maps  and
       rejects	non-existent  recipients.  See	also  the  relay  domains  address  class  in the
       ADDRESS_CLASS_README file.

       Note: Postfix will not automatically forward mail for domains that  list  this  system  as
       their  primary  or backup MX host. See the permit_mx_backup restriction in the postconf(5)
       manual page.

       Specify a list of host or domain  names,  "/file/name"  patterns  or  "type:table"  lookup
       tables,	separated  by commas and/or whitespace.  Continue long lines by starting the next
       line with whitespace. A "/file/name" pattern is replaced by its contents;  a  "type:table"
       lookup  table  is matched when a (parent) domain appears as lookup key. Specify "!pattern"
       to exclude a domain from the list. The form "!/file/name" is  supported	only  in  Postfix
       version 2.4 and later.

relay_domains_reject_code (default: 554)
       The  numerical  Postfix SMTP server response code when a client request is rejected by the
       reject_unauth_destination recipient restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

relay_recipient_maps (default: empty)
       Optional lookup tables with all valid addresses in the domains that match  $relay_domains.
       Specify @domain as a wild-card for domains that have no valid recipient list, and become a
       source of backscatter mail: Postfix accepts spam  for  non-existent  recipients	and  then
       floods	innocent  people  with	undeliverable  mail.   Technically,  tables  listed  with
       $relay_recipient_maps are used as lists: Postfix needs to know only if a lookup string  is
       found or not, but it does not use the result from table lookup.

       If  this  parameter is non-empty, then the Postfix SMTP server will reject mail to unknown
       relay users. This feature is off by default.

       See also the relay domains address class in the ADDRESS_CLASS_README file.

       Example:

       relay_recipient_maps = hash:/etc/postfix/relay_recipients

       This feature is available in Postfix 2.0 and later.

relay_transport (default: relay)
       The default mail delivery transport  and  next-hop  destination	for  remote  delivery  to
       domains	listed with $relay_domains. In order of decreasing precedence, the nexthop desti-
       nation is taken from $relay_transport,  $sender_dependent_relayhost_maps,  $relayhost,  or
       from the recipient domain. This information can be overruled with the transport(5) table.

       Specify	a  string  of  the  form transport:nexthop, where transport is the name of a mail
       delivery transport defined in master.cf.  The :nexthop destination is optional; its syntax
       is documented in the manual page of the corresponding delivery agent.

       See also the relay domains address class in the ADDRESS_CLASS_README file.

       This feature is available in Postfix 2.0 and later.

relayhost (default: empty)
       The  next-hop  destination  of  non-local  mail;  overrides non-local domains in recipient
       addresses.   This   information	 is   overruled   with	 relay_transport,   sender_depen-
       dent_default_transport_maps,  default_transport,  sender_dependent_relayhost_maps and with
       the transport(5) table.

       On an intranet, specify the organizational domain name. If your internal DNS  uses  no  MX
       records, specify the name of the intranet gateway host instead.

       In  the	case  of  SMTP,  specify a domain name, hostname, hostname:port, [hostname]:port,
       [hostaddress] or [hostaddress]:port. The form [hostname] turns off MX lookups.

       If you're connected via UUCP, see the UUCP_README file for useful information.

       Examples:

       relayhost = $mydomain
       relayhost = [gateway.example.com]
       relayhost = uucphost
       relayhost = [an.ip.add.ress]

relocated_maps (default: empty)
       Optional lookup tables with new contact information for users or domains  that  no  longer
       exist.  The table format and lookups are documented in relocated(5).

       If  you	use this feature, run "postmap /etc/postfix/relocated" to build the necessary DBM
       or DB file after change, then "postfix reload" to make the changes visible.

       Examples:

       relocated_maps = dbm:/etc/postfix/relocated
       relocated_maps = hash:/etc/postfix/relocated

remote_header_rewrite_domain (default: empty)
       Don't rewrite message headers from remote clients at all when  this  parameter  is  empty;
       otherwise,  rewrite  message  headers  and  append the specified domain name to incomplete
       addresses.  The local_header_rewrite_clients parameter controls what clients Postfix  con-
       siders local.

       Examples:

       The  safe setting: append "domain.invalid" to incomplete header addresses from remote SMTP
       clients, so that those addresses cannot be confused with local addresses.

	   remote_header_rewrite_domain = domain.invalid

       The default, purist, setting: don't rewrite headers from remote clients at all.

	   remote_header_rewrite_domain =

require_home_directory (default: no)
       Require that a  local(8)  recipient's  home  directory  exists  before  mail  delivery  is
       attempted.  By  default	this  test  is	disabled.  It can be useful for environments that
       import home directories to the mail server  (IMPORTING  HOME  DIRECTORIES  IS  NOT  RECOM-
       MENDED).

reset_owner_alias (default: no)
       Reset  the  local(8)  delivery  agent's idea of the owner-alias attribute, when delivering
       mail to a child alias that does not have its own owner alias.

       This feature is available in Postfix 2.8 and  later.  With  older  Postfix  releases,  the
       behavior is as if this parameter is set to "yes".

       As  documented  in  aliases(5), when an alias name has a companion alias named owner-name,
       delivery errors will be reported to the owner alias instead of the sender. This configura-
       tion is recommended for mailing lists.

       A  less	known  property  of  the owner alias is that it also forces the local(8) delivery
       agent to write local and remote addresses from  alias  expansion  to  a	new  queue  file,
       instead of attempting to deliver mail to local addresses as soon as they come out of alias
       expansion.

       Writing local addresses from alias expansion to a new queue file allows	for  robust  han-
       dling  of temporary delivery errors: errors with one local member have no effect on deliv-
       eries to other members of the list.  On the other hand, delivery  to  local  addresses  as
       soon  as  they  come  out  of alias expansion is fragile: a temporary error with one local
       address from alias expansion will cause the entire alias to be expanded	repeatedly  until
       the  error  goes away, or until the message expires in the queue.  In that case, a problem
       with one list member results in multiple message deliveries to other list members.

       The default behavior of Postfix 2.8 and later is to keep the owner-alias attribute of  the
       parent  alias,  when  delivering  mail  to  a child alias that does not have its own owner
       alias. Then, local addresses from that child alias will be written to a	new  queue  file,
       and  a  temporary  error  with one local address will not affect delivery to other mailing
       list members.

       Unfortunately, older Postfix releases reset the owner-alias attribute when delivering mail
       to a child alias that does not have its own owner alias.  The local(8) delivery agent then
       attempts to deliver local addresses as soon as they come out of child alias expansion.  If
       delivery to any address from child alias expansion fails with a temporary error condition,
       the entire mailing list may be expanded repeatedly until the mail expires  in  the  queue,
       resulting in multiple deliveries of the same message to mailing list members.

resolve_dequoted_address (default: yes)
       Resolve a recipient address safely instead of correctly, by looking inside quotes.

       By  default,  the Postfix address resolver does not quote the address localpart as per RFC
       822, so that additional @ or % or !  operators remain visible. This behavior is	safe  but
       it is also technically incorrect.

       If  you	specify  "resolve_dequoted_address = no", then the Postfix resolver will not know
       about additional @ etc. operators in the address localpart. This opens  opportunities  for
       obscure	mail relay attacks with user@domain@domain addresses when Postfix provides backup
       MX service for Sendmail systems.

resolve_null_domain (default: no)
       Resolve an address that ends in the "@" null domain as if the local hostname  were  speci-
       fied, instead of rejecting the address as invalid.

       This  feature  is available in Postfix 2.1 and later.  Earlier versions always resolve the
       null domain as the local hostname.

       The Postfix SMTP server uses this feature to reject mail from or to addresses that end  in
       the "@" null domain, and from addresses that rewrite into a form that ends in the "@" null
       domain.

resolve_numeric_domain (default: no)
       Resolve "user@ipaddress" as  "user@[ipaddress]",  instead  of  rejecting  the  address  as
       invalid.

       This feature is available in Postfix 2.3 and later.

rewrite_service_name (default: rewrite)
       The  name  of  the  address rewriting service. This service rewrites addresses to standard
       form and resolves them to a (delivery method, next-hop host, recipient) triple.

       This feature is available in Postfix 2.0 and later.

sample_directory (default: /etc/postfix)
       The name of the directory with example Postfix configuration files.  Starting with Postfix
       2.1, these files have been replaced with the postconf(5) manual page.

send_cyrus_sasl_authzid (default: no)
       When authenticating to a remote SMTP or LMTP server with the default setting "no", send no
       SASL authoriZation ID (authzid); send only the SASL authentiCation ID (authcid)	plus  the
       authcid's password.

       The  non-default  setting  "yes"  enables  the  behavior of older Postfix versions.  These
       always send a SASL authzid that is equal to the SASL authcid, but this causes  inter-oper-
       ability problems with some SMTP servers.

       This feature is available in Postfix 2.4.4 and later.

sender_based_routing (default: no)
       This  parameter	should not be used. It was replaced by sender_dependent_relayhost_maps in
       Postfix version 2.3.

sender_bcc_maps (default: empty)
       Optional BCC (blind carbon-copy) address lookup tables, indexed by  sender  address.   The
       BCC address (multiple results are not supported) is added when mail enters from outside of
       Postfix.

       This feature is available in Postfix 2.1 and later.

       The table search order is as follows:

       o      Look up the "user+extension@domain.tld"  address	including  the	optional  address
	      extension.

       o      Look up the "user@domain.tld" address without the optional address extension.

       o      Look up the "user+extension" address local part when the sender domain equals $myo-
	      rigin, $mydestination, $inet_interfaces or $proxy_interfaces.

       o      Look up the "user" address local part when  the  sender  domain  equals  $myorigin,
	      $mydestination, $inet_interfaces or $proxy_interfaces.

       o      Look up the "@domain.tld" part.

       Specify	the  types  and names of databases to use.  After change, run "postmap /etc/post-
       fix/sender_bcc".

       Note: if mail to the BCC address bounces it will be returned to the sender.

       Note: automatic BCC recipients are produced only for new mail.	To  avoid  mailer  loops,
       automatic  BCC  recipients  are	not  generated after Postfix forwards mail internally, or
       after Postfix generates mail itself.

       Example:

       sender_bcc_maps = hash:/etc/postfix/sender_bcc

sender_canonical_classes (default: envelope_sender, header_sender)
       What  addresses	are  subject  to  sender_canonical_maps  address  mapping.   By  default,
       sender_canonical_maps  address  mapping	is  applied  to envelope sender addresses, and to
       header sender addresses.

       Specify one or more of: envelope_sender, header_sender

       This feature is available in Postfix 2.2 and later.

sender_canonical_maps (default: empty)
       Optional address mapping lookup tables for envelope and header sender addresses.  The  ta-
       ble format and lookups are documented in canonical(5).

       Example:    you	  want	  to   rewrite	 the   SENDER	address   "user@ugly.domain"   to
       "user@pretty.domain", while still being	able  to  send	mail  to  the  RECIPIENT  address
       "user@ugly.domain".

       Note: $sender_canonical_maps is processed before $canonical_maps.

       Example:

       sender_canonical_maps = hash:/etc/postfix/sender_canonical

sender_dependent_default_transport_maps (default: empty)
       A sender-dependent override for the global default_transport parameter setting. The tables
       are searched by the envelope sender address and @domain. A lookup result of  DUNNO  termi-
       nates  the search without overriding the global default_transport parameter setting.  This
       information is overruled with the transport(5) table.

       Note: this overrides default_transport, not transport_maps,  and  therefore  the  expected
       syntax is that of default_transport, not the syntax of transport_maps.  Specifically, this
       does not support the transport_maps syntax for null transport, null nexthop, or null email
       addresses.

       For  safety  reasons, this feature does not allow $number substitutions in regular expres-
       sion maps.

       This feature is available in Postfix 2.7 and later.

sender_dependent_relayhost_maps (default: empty)
       A sender-dependent override for the global relayhost parameter  setting.  The  tables  are
       searched  by  the envelope sender address and @domain. A lookup result of DUNNO terminates
       the search without overriding the global relayhost  parameter  setting  (Postfix  2.6  and
       later).	  This	  information	 is   overruled   with	 relay_transport,   sender_depen-
       dent_default_transport_maps, default_transport and with the transport(5) table.

       For safety reasons, this feature does not allow $number substitutions in  regular  expres-
       sion maps.

       This feature is available in Postfix 2.3 and later.

sendmail_path (default: see postconf -d output)
       A  Sendmail  compatibility  feature that specifies the location of the Postfix sendmail(1)
       command. This command can be used to submit mail into the Postfix queue.

service_throttle_time (default: 60s)
       How long the Postfix master(8) waits before forking a server that appears to  be  malfunc-
       tioning.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

setgid_group (default: postdrop)
       The group ownership of set-gid Postfix commands and of group-writable Postfix directories.
       When  this  parameter  value is changed you need to re-run "postfix set-permissions" (with
       Postfix version 2.0 and earlier: "/etc/postfix/post-install set-permissions".

show_user_unknown_table_name (default: yes)
       Display the name of the recipient table in the "User unknown" responses.  The extra detail
       makes trouble shooting easier but also reveals information that is nobody elses business.

       This feature is available in Postfix 2.0 and later.

showq_service_name (default: showq)
       The name of the showq(8) service. This service produces mail queue status reports.

       This feature is available in Postfix 2.0 and later.

smtp_address_preference (default: ipv6)
       The  address  type  ("ipv6", "ipv4" or "any") that the Postfix SMTP client will try first,
       when a destination has IPv6 and IPv4 addresses with equal MX preference. This feature  has
       no effect unless the inet_protocols setting enables both IPv4 and IPv6.

       This feature is available in Postfix 2.8 and later.

smtp_always_send_ehlo (default: yes)
       Always send EHLO at the start of an SMTP session.

       With  "smtp_always_send_ehlo  = no", Postfix sends EHLO only when the word "ESMTP" appears
       in the server greeting banner (example: 220 spike.porcupine.org ESMTP Postfix).

smtp_bind_address (default: empty)
       An optional numerical network address that the Postfix SMTP client  should  bind  to  when
       making an IPv4 connection.

       This  can be specified in the main.cf file for all SMTP clients, or it can be specified in
       the master.cf file for a specific client, for example:

	   /etc/postfix/master.cf:
	       smtp ... smtp -o smtp_bind_address=11.22.33.44

       Note 1: when inet_interfaces specifies no more than one IPv4 address, and that address  is
       a  non-loopback address, it is automatically used as the smtp_bind_address.  This supports
       virtual IP hosting, but can be a problem on multi-homed firewalls. See the inet_interfaces
       documentation for more detail.

       Note 2: address information may be enclosed inside [], but this form is not required here.

smtp_bind_address6 (default: empty)
       An  optional  numerical	network  address that the Postfix SMTP client should bind to when
       making an IPv6 connection.

       This feature is available in Postfix 2.2 and later.

       This can be specified in the main.cf file for all SMTP clients, or it can be specified  in
       the master.cf file for a specific client, for example:

	   /etc/postfix/master.cf:
	       smtp ... smtp -o smtp_bind_address6=1:2:3:4:5:6:7:8

       Note  1: when inet_interfaces specifies no more than one IPv6 address, and that address is
       a non-loopback address, it is automatically used as the smtp_bind_address6.  This supports
       virtual IP hosting, but can be a problem on multi-homed firewalls. See the inet_interfaces
       documentation for more detail.

       Note 2: address information may be enclosed inside [], but this form  is  not  recommended
       here.

smtp_body_checks (default: empty)
       Restricted  body_checks(5)  tables for the Postfix SMTP client.	These tables are searched
       while mail is being delivered.  Actions that change the delivery time or  destination  are
       not available.

       This feature is available in Postfix 2.5 and later.

smtp_cname_overrides_servername (default: version dependent)
       Allow  DNS  CNAME records to override the servername that the Postfix SMTP client uses for
       logging, SASL password lookup, TLS policy decisions, or TLS certificate verification.  The
       value  "no"  hardens Postfix smtp_tls_per_site hostname-based policies against false host-
       name information in DNS CNAME records, and makes SASL  password	file  lookups  more  pre-
       dictable. This is the default setting as of Postfix 2.3.

       This feature is available in Postfix 2.2.9 and later.

smtp_connect_timeout (default: 30s)
       The  SMTP  client  time	limit for completing a TCP connection, or zero (use the operating
       system built-in time limit).

       When no connection can be made within the deadline, the Postfix SMTP client tries the next
       address on the mail exchanger list. Specify 0 to disable the time limit (i.e. use whatever
       timeout is implemented by the operating system).

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

smtp_connection_cache_destinations (default: empty)
       Permanently enable SMTP connection caching for the specified destinations.  With SMTP con-
       nection caching, a connection is not closed immediately after completion of a mail  trans-
       action.	 Instead, the connection is kept open for up to $smtp_connection_cache_time_limit
       seconds.  This allows connections to be reused for other deliveries, and can improve  mail
       delivery performance.

       Specify a comma or white space separated list of destinations or pseudo-destinations:

       o      if  mail	is  sent  without  a relay host: a domain name (the right-hand side of an
	      email address, without the [] around a numeric IP address),

       o      if mail is sent via a relay host: a relay host name (without [] or non-default  TCP
	      port), as specified in main.cf or in the transport map,

       o      if mail is sent via a UNIX-domain socket: a pathname (without the unix: prefix),

       o      a /file/name with domain names and/or relay host names as defined above,

       o      a  "type:table"  with  domain  names and/or relay host names on the left-hand side.
	      The right-hand side result from "type:table" lookups is ignored.

       This feature is available in Postfix 2.2 and later.

smtp_connection_cache_on_demand (default: yes)
       Temporarily enable SMTP connection caching while a destination has a high volume  of  mail
       in the active queue.  With SMTP connection caching, a connection is not closed immediately
       after completion of a mail transaction.	Instead, the connection is kept open  for  up  to
       $smtp_connection_cache_time_limit seconds.  This allows connections to be reused for other
       deliveries, and can improve mail delivery performance.

       This feature is available in Postfix 2.2 and later.

smtp_connection_cache_reuse_limit (default: 10)
       When SMTP connection caching is enabled, the number of times that an SMTP session  may  be
       reused before it is closed.

       This  feature  is available in Postfix 2.2. In Postfix 2.3 it is replaced by $smtp_connec-
       tion_reuse_time_limit.

smtp_connection_cache_time_limit (default: 2s)
       When SMTP connection caching is enabled, the amount of time that  an  unused  SMTP  client
       socket  is kept open before it is closed.  Do not specify larger values without permission
       from the remote sites.

       This feature is available in Postfix 2.2 and later.

smtp_connection_reuse_time_limit (default: 300s)
       The amount of time during which Postfix will use an SMTP connection repeatedly.	The timer
       starts  when  the connection is initiated (i.e. it includes the connect, greeting and helo
       latency, in addition to the latencies of subsequent mail delivery transactions).

       This feature addresses a performance stability problem  with  remote  SMTP  servers.  This
       problem is not specific to Postfix: it can happen when any MTA sends large amounts of SMTP
       email to a site that has multiple MX hosts.

       The problem starts when one of a set of MX hosts  becomes  slower  than	the  rest.   Even
       though  SMTP clients connect to fast and slow MX hosts with equal probability, the slow MX
       host ends up with more simultaneous inbound connections than the faster MX hosts,  because
       the slow MX host needs more time to serve each client request.

       The  slow  MX  host becomes a connection attractor.  If one MX host becomes N times slower
       than the rest, it dominates mail delivery latency unless there are more	than  N  fast  MX
       hosts  to  counter  the	effect. And if the number of MX hosts is smaller than N, the mail
       delivery latency becomes effectively that of the slowest MX host divided by the total num-
       ber of MX hosts.

       The  solution  uses connection caching in a way that differs from Postfix version 2.2.  By
       limiting the amount of time during which a connection can be used repeatedly  (instead  of
       limiting  the  number of deliveries over that connection), Postfix not only restores fair-
       ness in the distribution of simultaneous connections across a set of  MX  hosts,  it  also
       favors deliveries over connections that perform well, which is exactly what we want.

       The default reuse time limit, 300s, is comparable to the various smtp transaction timeouts
       which are fair estimates of maximum excess latency for a slow delivery.	Note  that  hosts
       may  accept  thousands  of messages over a single connection within the default connection
       reuse time limit. This number is much larger than the default Postfix version 2.2 limit of
       10  messages  per  cached  connection.  It may prove necessary to lower the limit to avoid
       interoperability issues with MTAs that exhibit bugs when many messages are delivered via a
       single  connection.  A lower reuse time limit risks losing the benefit of connection reuse
       when the average connection and mail delivery latency exceeds the reuse time limit.

       This feature is available in Postfix 2.3 and later.

smtp_data_done_timeout (default: 600s)
       The SMTP client time limit for  sending	the  SMTP  ".",  and  for  receiving  the  server
       response.

       When no response is received within the deadline, a warning is logged that the mail may be
       delivered multiple times.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

smtp_data_init_timeout (default: 120s)
       The SMTP client time limit for sending the SMTP DATA command, and for receiving the server
       response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

smtp_data_xfer_timeout (default: 180s)
       The  SMTP  client  time	limit  for sending the SMTP message content.  When the connection
       makes no progress for more than $smtp_data_xfer_timeout seconds the  Postfix  SMTP  client
       terminates the transfer.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_defer_if_no_mx_address_found (default: no)
       Defer mail delivery when no MX record resolves to an IP address.

       The default (no) is to return the mail as undeliverable. With older Postfix  versions  the
       default	was to keep trying to deliver the mail until someone fixed the MX record or until
       the mail was too old.

       Note: Postfix always ignores MX records with equal or worse preference than the local  MTA
       itself.

       This feature is available in Postfix 2.1 and later.

smtp_destination_concurrency_limit (default: $default_destination_concurrency_limit)
       The  maximal  number  of  parallel deliveries to the same destination via the smtp message
       delivery transport. This limit is enforced by the  queue  manager.  The	message  delivery
       transport name is the first field in the entry in the master.cf file.

smtp_destination_recipient_limit (default: $default_destination_recipient_limit)
       The maximal number of recipients per message for the smtp message delivery transport. This
       limit is enforced by the queue manager. The message delivery transport name is  the  first
       field in the entry in the master.cf file.

       Setting	this  parameter  to  a value of 1 changes the meaning of smtp_destination_concur-
       rency_limit from concurrency per domain into concurrency per recipient.

smtp_discard_ehlo_keyword_address_maps (default: empty)
       Lookup tables, indexed by the remote SMTP server address, with case insensitive	lists  of
       EHLO  keywords (pipelining, starttls, auth, etc.) that the Postfix SMTP client will ignore
       in the EHLO response  from  a  remote  SMTP  server.  See  smtp_discard_ehlo_keywords  for
       details. The table is not indexed by hostname for consistency with smtpd_discard_ehlo_key-
       word_address_maps.

       This feature is available in Postfix 2.2 and later.

smtp_discard_ehlo_keywords (default: empty)
       A case insensitive list of EHLO keywords (pipelining, starttls, auth, etc.) that the Post-
       fix SMTP client will ignore in the EHLO response from a remote SMTP server.

       This feature is available in Postfix 2.2 and later.

       Notes:

       o      Specify the silent-discard pseudo keyword to prevent this action from being logged.

       o      Use  the	smtp_discard_ehlo_keyword_address_maps	feature  to discard EHLO keywords
	      selectively.

smtp_dns_resolver_options (default: empty)
       DNS Resolver options for the Postfix SMTP client.  Specify zero or more of  the	following
       options,  separated by comma or whitespace.  Option names are case-sensitive. Some options
       refer to domain names that are specified in the file /etc/resolv.conf or equivalent.

       res_defnames
	      Append the current domain name to single-component names (those that do not contain
	      a  "." character). This can produce incorrect results, and is the hard-coded behav-
	      ior prior to Postfix 2.8.

       res_dnsrch
	      Search for host names in the current domain and in parent domains. This can produce
	      incorrect results and is therefore not recommended.

       This feature is available in Postfix 2.8 and later.

smtp_enforce_tls (default: no)
       Enforcement mode: require that remote SMTP servers use TLS encryption, and never send mail
       in the clear.  This also requires that the remote SMTP server hostname matches the  infor-
       mation  in  the remote server certificate, and that the remote SMTP server certificate was
       issued by a CA that is trusted by the Postfix SMTP client. If the certificate doesn't ver-
       ify or the hostname doesn't match, delivery is deferred and mail stays in the queue.

       The server hostname is matched against all names provided as dNSNames in the SubjectAlter-
       nativeName.  If no dNSNames are specified, the CommonName is checked.  The behavior may be
       changed with the smtp_tls_enforce_peername option.

       This  option  is  useful  only  if  you	are definitely sure that you will only connect to
       servers that support RFC 2487 _and_ that provide valid server certificates.   Typical  use
       is for clients that send all their email to a dedicated mailhub.

       This  feature  is  available  in  Postfix  2.2  and  later. With Postfix 2.3 and later use
       smtp_tls_security_level instead.

smtp_fallback_relay (default: $fallback_relay)
       Optional list of relay hosts for SMTP  destinations  that  can't  be  found  or	that  are
       unreachable. With Postfix 2.2 and earlier this parameter is called fallback_relay.

       By  default,  mail is returned to the sender when a destination is not found, and delivery
       is deferred when a destination is unreachable.

       The fallback relays  must  be  SMTP  destinations.  Specify  a  domain,	host,  host:port,
       [host]:port,  [address]	or  [address]:port; the form [host] turns off MX lookups.  If you
       specify multiple SMTP destinations, Postfix will try them in the specified order.

       To prevent mailer loops between MX hosts and fall-back  hosts,  Postfix	version  2.2  and
       later  will  not use the fallback relays for destinations that it is MX host for (assuming
       DNS lookup is turned on).

smtp_generic_maps (default: empty)
       Optional lookup tables that perform address rewriting in the  SMTP  client,  typically  to
       transform  a  locally valid address into a globally valid address when sending mail across
       the Internet.  This is needed when the local machine does not have its own Internet domain
       name, but uses something like localdomain.local instead.

       The  table  format  and	lookups  are  documented in generic(5); examples are shown in the
       ADDRESS_REWRITING_README and STANDARD_CONFIGURATION_README documents.

       This feature is available in Postfix 2.2 and later.

smtp_header_checks (default: empty)
       Restricted header_checks(5) tables for the Postfix SMTP client.	These tables are searched
       while  mail  is being delivered.  Actions that change the delivery time or destination are
       not available.

       This feature is available in Postfix 2.5 and later.

smtp_helo_name (default: $myhostname)
       The hostname to send in the SMTP EHLO or HELO command.

       The default value is the machine hostname.  Specify a hostname or [ip.add.re.ss].

       This information can be specified in the main.cf file for all SMTP clients, or it  can  be
       specified in the master.cf file for a specific client, for example:

	   /etc/postfix/master.cf:
	       mysmtp ... smtp -o smtp_helo_name=foo.bar.com

       This feature is available in Postfix 2.0 and later.

smtp_helo_timeout (default: 300s)
       The  SMTP  client  time	limit for sending the HELO or EHLO command, and for receiving the
       initial server response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

smtp_host_lookup (default: dns)
       What mechanisms the Postfix SMTP client uses to look up a host's IP address.  This parame-
       ter is ignored when DNS lookups are disabled (see: disable_dns_lookups).

       Specify one of the following:

       dns    Hosts can be found in the DNS (preferred).

       native Use the native naming service only (nsswitch.conf, or equivalent mechanism).

       dns, native
	      Use the native service for hosts not found in the DNS.

       This feature is available in Postfix 2.1 and later.

smtp_line_length_limit (default: 990)
       The maximal length of message header and body lines  that  Postfix  will  send  via  SMTP.
       Longer  lines are broken by inserting "<CR><LF><SPACE>". This minimizes the damage to MIME
       formatted mail.

       By default, the line length is limited to 990 characters, because some server  implementa-
       tions cannot receive mail with long lines.

smtp_mail_timeout (default: 300s)
       The SMTP client time limit for sending the MAIL FROM command, and for receiving the server
       response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

smtp_mime_header_checks (default: empty)
       Restricted  mime_header_checks(5)  tables  for  the  Postfix SMTP client. These tables are
       searched while mail is being delivered.	Actions that change the delivery time or destina-
       tion are not available.

       This feature is available in Postfix 2.5 and later.

smtp_mx_address_limit (default: 5)
       The maximal number of MX (mail exchanger) IP addresses that can result from mail exchanger
       lookups, or zero (no limit). Prior to Postfix version 2.3,  this  limit	was  disabled  by
       default.

       This feature is available in Postfix 2.1 and later.

smtp_mx_session_limit (default: 2)
       The maximal number of SMTP sessions per delivery request before giving up or delivering to
       a fall-back relay host, or zero (no limit). This restriction ignores sessions that fail to
       complete the SMTP initial handshake (Postfix version 2.2 and earlier) or that fail to com-
       plete the EHLO and TLS handshake (Postfix version 2.3 and later).

       This feature is available in Postfix 2.1 and later.

smtp_nested_header_checks (default: empty)
       Restricted nested_header_checks(5) tables for the Postfix SMTP client.  These  tables  are
       searched while mail is being delivered.	Actions that change the delivery time or destina-
       tion are not available.

       This feature is available in Postfix 2.5 and later.

smtp_never_send_ehlo (default: no)
       Never send EHLO at the start of an SMTP session. See also the smtp_always_send_ehlo param-
       eter.

smtp_pix_workaround_delay_time (default: 10s)
       How long the Postfix SMTP client pauses before sending ".<CR><LF>" in order to work around
       the PIX firewall "<CR><LF>.<CR><LF>" bug.

       Choosing a too short time makes this workaround ineffective when  sending  large  messages
       over slow network connections.

smtp_pix_workaround_maps (default: empty)
       Lookup tables, indexed by the remote SMTP server address, with per-destination workarounds
       for CISCO PIX firewall bugs.  The table is not indexed by hostname  for	consistency  with
       smtp_discard_ehlo_keyword_address_maps.

       This feature is available in Postfix 2.4 and later.

smtp_pix_workaround_threshold_time (default: 500s)
       How long a message must be queued before the Postfix SMTP client turns on the PIX firewall
       "<CR><LF>.<CR><LF>" bug workaround for delivery through firewalls with "smtp  fixup"  mode
       turned on.

       By  default,  the  workaround is turned off for mail that is queued for less than 500 sec-
       onds. In other words, the workaround  is  normally  turned  off	for  the  first  delivery
       attempt.

       Specify	0  to  enable  the PIX firewall "<CR><LF>.<CR><LF>" bug workaround upon the first
       delivery attempt.

smtp_pix_workarounds (default: disable_esmtp, delay_dotcrlf)
       A list that specifies zero or more workarounds for CISCO PIX firewall  bugs.  These  work-
       arounds	are  implemented  by  the  Postfix SMTP client. Workaround names are separated by
       comma or space, and are case insensitive.  This parameter setting can  be  overruled  with
       per-destination smtp_pix_workaround_maps settings.

       delay_dotcrlf
	      Insert  a  delay	before	sending ".<CR><LF>" after the end of the message content.
	      The delay is  subject  to  the  smtp_pix_workaround_delay_time  and  smtp_pix_work-
	      around_threshold_time parameter settings.

       disable_esmtp
	      Disable all extended SMTP commands: send HELO instead of EHLO.

       This  feature  is  available  in Postfix 2.4 and later. The default settings are backwards
       compatible with earlier Postfix versions.

smtp_quit_timeout (default: 300s)
       The SMTP client time limit for sending the QUIT command,  and  for  receiving  the  server
       response.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_quote_rfc821_envelope (default: yes)
       Quote addresses in SMTP MAIL FROM and RCPT TO commands  as  required  by  RFC  2821.  This
       includes putting quotes around an address localpart that ends in ".".

       The  default is to comply with RFC 2821. If you have to send mail to a broken SMTP server,
       configure a special SMTP client in master.cf:

	   /etc/postfix/master.cf:
	       broken-smtp . . . smtp -o smtp_quote_rfc821_envelope=no

       and route mail for the destination in question to the "broken-smtp" message delivery  with
       a transport(5) table.

       This feature is available in Postfix 2.1 and later.

smtp_randomize_addresses (default: yes)
       Randomize  the order of equal-preference MX host addresses.  This is a performance feature
       of the Postfix SMTP client.

smtp_rcpt_timeout (default: 300s)
       The SMTP client time limit for sending the SMTP RCPT TO command,  and  for  receiving  the
       server response.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_reply_filter (default: empty)
       A mechanism to transform replies from remote SMTP servers one line at a time.  This  is	a
       last-resort tool to work around server replies that break inter-operability with the Post-
       fix SMTP client.  Other uses involve fault injection to test Postfix's handling of invalid
       responses.

       Notes:

       o      In  the  case  of  a multi-line reply, the Postfix SMTP client uses the final reply
	      line's numerical SMTP reply code and enhanced status code.

       o      The numerical SMTP reply code (XYZ) takes precedence over the enhanced status  code
	      (X.Y.Z).	 When  the enhanced status code initial digit differs from the SMTP reply
	      code initial digit, or when no enhanced status code is present,  the  Postfix  SMTP
	      client uses a generic enhanced status code (X.0.0) instead.

       Specify	the name of a "type:table" lookup table. The search string is a single SMTP reply
       line as received from the remote SMTP  server,  except  that  the  trailing  <CR><LF>  are
       removed.

       Examples:

       /etc/postfix/main.cf:
	   smtp_reply_filter = pcre:/etc/postfix/reply_filter

       /etc/postfix/reply_filter:
	   # Transform garbage into "250-filler..." so that it looks like
	   # one line from a multi-line reply. It does not matter what we
	   # substitute here as long it has the right syntax.  The Postfix
	   # SMTP client will use the final line's numerical SMTP reply
	   # code and enhanced status code.
	   !/^([2-5][0-9][0-9]($|[- ]))/ 250-filler for garbage

       This feature is available in Postfix 2.7.

smtp_rset_timeout (default: 20s)
       The  SMTP  client  time	limit  for sending the RSET command, and for receiving the server
       response. The SMTP client sends RSET in order to finish a recipient address probe,  or  to
       verify that a cached session is still usable.

       This feature is available in Postfix 2.1 and later.

smtp_sasl_auth_cache_name (default: empty)
       An  optional  table  to prevent repeated SASL authentication failures with the same remote
       SMTP server hostname, username and password. Each  table  (key,	value)	pair  contains	a
       server  name,  a  username and password, and the full server response. This information is
       stored when a remote SMTP server rejects an authentication attempt with a 535 reply  code.
       As  long  as  the  smtp_sasl_password_maps  information does no change, and as long as the
       smtp_sasl_auth_cache_name information does not expire (see smtp_sasl_auth_cache_time)  the
       Postfix SMTP client avoids SASL authentication attempts with the same server, username and
       password,   and	 instead   bounces   or   defers   mail   as	controlled    with    the
       smtp_sasl_auth_soft_bounce configuration parameter.

       Use  a  per-destination	delivery concurrency of 1 (for example, "smtp_destination_concur-
       rency_limit = 1", "relay_destination_concurrency_limit =  1",  etc.),  otherwise  multiple
       delivery agents may experience a login failure at the same time.

       The  table  must be accessed via the proxywrite service, i.e. the map name must start with
       "proxy:". The table should be stored under the directory specified with the data_directory
       parameter.

       This feature uses cryptographic hashing to protect plain-text passwords, and requires that
       Postfix is compiled with TLS support.

       Example:

       smtp_sasl_auth_cache_name = proxy:btree:/var/db/postfix/sasl_auth_cache

       This feature is available in Postfix 2.5 and later.

smtp_sasl_auth_cache_time (default: 90d)
       The maximal age of an smtp_sasl_auth_cache_name entry before it is removed.

       This feature is available in Postfix 2.5 and later.

smtp_sasl_auth_enable (default: no)
       Enable SASL authentication in the Postfix SMTP  client.	 By  default,  the  Postfix  SMTP
       client uses no authentication.

       Example:

       smtp_sasl_auth_enable = yes

smtp_sasl_auth_soft_bounce (default: yes)
       When  a	remote	SMTP  server rejects a SASL authentication request with a 535 reply code,
       defer mail delivery instead of returning mail as undeliverable. The  latter  behavior  was
       hard-coded prior to Postfix version 2.5.

       Note:  the  setting "yes" overrides the global soft_bounce parameter, but the setting "no"
       does not.

       Example:

       # Default as of Postfix 2.5
       smtp_sasl_auth_soft_bounce = yes
       # The old hard-coded default
       smtp_sasl_auth_soft_bounce = no

       This feature is available in Postfix 2.5 and later.

smtp_sasl_mechanism_filter (default: empty)
       If non-empty, a Postfix SMTP client filter for the remote SMTP server's	list  of  offered
       SASL mechanisms.  Different client and server implementations may support different mecha-
       nism lists. By default, the Postfix SMTP client will use  the  intersection  of	the  two.
       smtp_sasl_mechanism_filter  further  restricts what server mechanisms the client will take
       into consideration.

       Specify mechanism names, "/file/name" patterns or "type:table" lookup tables.  The  right-
       hand  side  result  from  "type:table" lookups is ignored. Specify "!pattern" to exclude a
       mechanism name from the list. The form "!/file/name" is supported only in Postfix  version
       2.4 and later.

       This feature is available in Postfix 2.2 and later.

       Examples:

       smtp_sasl_mechanism_filter = plain, login
       smtp_sasl_mechanism_filter = /etc/postfix/smtp_mechs
       smtp_sasl_mechanism_filter = !gssapi, !login, static:rest

smtp_sasl_password_maps (default: empty)
       Optional SMTP client lookup tables with one username:password entry per remote hostname or
       domain, or sender address when sender-dependent authentication is enabled.   If	no  user-
       name:password  entry  is found, then the Postfix SMTP client will not attempt to authenti-
       cate to the remote host.

       The Postfix SMTP client opens the lookup table before going to chroot  jail,  so  you  can
       leave the password file in /etc/postfix.

smtp_sasl_path (default: empty)
       Implementation-specific	information  that  the	Postfix SMTP client passes through to the
       SASL plug-in implementation that is selected with smtp_sasl_type.  Typically  this  speci-
       fies the name of a configuration file or rendezvous point.

       This feature is available in Postfix 2.3 and later.

smtp_sasl_security_options (default: noplaintext, noanonymous)
       Postfix	SMTP  client  SASL security options; as of Postfix 2.3 the list of available fea-
       tures depends on the SASL client implementation that is selected with smtp_sasl_type.

       The following security features are defined for the cyrus client SASL implementation:

       Specify zero or more of the following:

       noplaintext
	      Disallow methods that use plaintext passwords.

       noactive
	      Disallow methods subject to active (non-dictionary) attack.

       nodictionary
	      Disallow methods subject to passive (dictionary) attack.

       noanonymous
	      Disallow methods that allow anonymous authentication.

       mutual_auth
	      Only allow methods that provide mutual authentication (not available with SASL ver-
	      sion 1).

       Example:

       smtp_sasl_security_options = noplaintext

smtp_sasl_tls_security_options (default: $smtp_sasl_security_options)
       The  SASL  authentication  security  options  that  the	Postfix  SMTP client uses for TLS
       encrypted SMTP sessions.

       This feature is available in Postfix 2.2 and later.

smtp_sasl_tls_verified_security_options (default: $smtp_sasl_tls_security_options)
       The SASL authentication security options  that  the  Postfix  SMTP  client  uses  for  TLS
       encrypted SMTP sessions with a verified server certificate.

       When  mail  is  sent to the public MX host for the recipient's domain, server certificates
       are by default optional, and delivery proceeds even if certificate verification fails. For
       delivery via a submission service that requires SASL authentication, it may be appropriate
       to send plaintext passwords only when the connection to the server is  strongly	encrypted
       and the server identity is verified.

       The  smtp_sasl_tls_verified_security_options  parameter	makes  it possible to only enable
       plaintext mechanisms when a secure connection  to  the  server  is  available.  Submission
       servers	subject to this policy must either have verifiable certificates or offer suitable
       non-plaintext SASL mechanisms.

       This feature is available in Postfix 2.6 and later.

smtp_sasl_type (default: cyrus)
       The SASL plug-in type that the Postfix SMTP client should  use  for  authentication.   The
       available types are listed with the "postconf -A" command.

       This feature is available in Postfix 2.3 and later.

smtp_send_xforward_command (default: no)
       Send  the  non-standard	XFORWARD  command  when  the  Postfix  SMTP  server EHLO response
       announces XFORWARD support.

       This allows an "smtp" delivery agent, used for injecting mail into a  content  filter,  to
       forward	the  name,  address, protocol and HELO name of the original client to the content
       filter and downstream queuing SMTP server. This	can  produce  more  useful  logging  than
       localhost[127.0.0.1] etc.

       This feature is available in Postfix 2.1 and later.

smtp_sender_dependent_authentication (default: no)
       Enable  sender-dependent authentication in the Postfix SMTP client; this is available only
       with SASL authentication, and disables SMTP connection caching to ensure  that  mail  from
       different senders will use the appropriate credentials.

       This feature is available in Postfix 2.3 and later.

smtp_skip_4xx_greeting (default: yes)
       Skip SMTP servers that greet with a 4XX status code (go away, try again later).

       By  default,  Postfix  moves on the next mail exchanger. Specify "smtp_skip_4xx_greeting =
       no" if Postfix should defer delivery immediately.

       This feature is available in Postfix 2.0 and earlier.  Later Postfix versions always  skip
       SMTP servers that greet with a 4XX status code.

smtp_skip_5xx_greeting (default: yes)
       Skip SMTP servers that greet with a 5XX status code (go away, do not try again later).

       By   default,  the  Postfix  SMTP  client  moves  on  the  next	mail  exchanger.  Specify
       "smtp_skip_5xx_greeting = no" if Postfix should bounce the mail immediately.  The  default
       setting is incorrect, but it is what a lot of people expect to happen.

smtp_skip_quit_response (default: yes)
       Do not wait for the response to the SMTP QUIT command.

smtp_starttls_timeout (default: 300s)
       Time  limit for Postfix SMTP client write and read operations during TLS startup and shut-
       down handshake procedures.

       This feature is available in Postfix 2.2 and later.

smtp_tls_CAfile (default: empty)
       A file containing CA certificates of root CAs trusted to sign either  remote  SMTP  server
       certificates  or  intermediate  CA  certificates.  These are loaded into memory before the
       smtp(8) client enters the chroot jail. If the number of trusted roots is  large,  consider
       using  smtp_tls_CApath  instead, but note that the latter directory must be present in the
       chroot jail if the smtp(8) client is chrooted. This file may also be used to  augment  the
       client  certificate  trust  chain, but it is best to include all the required certificates
       directly in $smtp_tls_cert_file.

       Specify "tls_append_default_CA = no" to prevent Postfix from appending the system-supplied
       default CAs and trusting third-party certificates.

       Example:

       smtp_tls_CAfile = /etc/postfix/CAcert.pem

       This feature is available in Postfix 2.2 and later.

smtp_tls_CApath (default: empty)
       Directory  with PEM format certificate authority certificates that the Postfix SMTP client
       uses to verify a remote SMTP server certificate.  Don't forget  to  create  the	necessary
       "hash" links with, for example, "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs".

       To  use	this  option in chroot mode, this directory (or a copy) must be inside the chroot
       jail.

       Specify "tls_append_default_CA = no" to prevent Postfix from appending the system-supplied
       default CAs and trusting third-party certificates.

       Example:

       smtp_tls_CApath = /etc/postfix/certs

       This feature is available in Postfix 2.2 and later.

smtp_tls_block_early_mail_reply (default: no)
       Try   to   detect   a  mail  hijacking  attack  based  on  a  TLS  protocol  vulnerability
       (CVE-2009-3555), where an attacker prepends malicious HELO, MAIL, RCPT, DATA commands to a
       Postfix	SMTP  client TLS session.  The attack would succeed with non-Postfix SMTP servers
       that reply to the malicious HELO, MAIL, RCPT, DATA commands after negotiating the  Postfix
       SMTP client TLS session.

       This feature is available in Postfix 2.7.

smtp_tls_cert_file (default: empty)
       File  with the Postfix SMTP client RSA certificate in PEM format.  This file may also con-
       tain the Postfix SMTP client private RSA key, and these may be the  same  as  the  Postfix
       SMTP server RSA certificate and key file.

       Do  not	configure  client certificates unless you must present client TLS certificates to
       one or more servers. Client certificates are not usually needed, and can cause problems in
       configurations that work well without them. The recommended setting is to let the defaults
       stand:

	   smtp_tls_cert_file =
	   smtp_tls_key_file =
	   smtp_tls_dcert_file =
	   smtp_tls_dkey_file =
	   smtp_tls_eccert_file =
	   smtp_tls_eckey_file =

       The best way to use the default settings is to comment out the above parameters in main.cf
       if present.

       To  enable  remote SMTP servers to verify the Postfix SMTP client certificate, the issuing
       CA certificates must be made available to the server. You should include the required cer-
       tificates  in  the client certificate file, the client certificate first, then the issuing
       CA(s) (bottom-up order).

       Example: the certificate for "client.example.com" was issued by	"intermediate  CA"  which
       itself  has  a  certificate  issued  by	"root  CA".  Create the client.pem file with "cat
       client_cert.pem intermediate_CA.pem root_CA.pem > client.pem".

       If you also want to verify remote SMTP server certificates issued by these  CAs,  you  can
       add  the CA certificates to the smtp_tls_CAfile, in which case it is not necessary to have
       them in the smtp_tls_cert_file, smtp_tls_dcert_file or smtp_tls_eccert_file.

       A certificate supplied here must be usable as an SSL client certificate and hence pass the
       "openssl verify -purpose sslclient ..." test.

       Example:

       smtp_tls_cert_file = /etc/postfix/client.pem

       This feature is available in Postfix 2.2 and later.

smtp_tls_cipherlist (default: empty)
       Obsolete  Postfix  < 2.3 control for the Postfix SMTP client TLS cipher list. As this fea-
       ture applies to all TLS security levels, it is easy to create  inter-operability  problems
       by  choosing  a non-default cipher list. Do not use a non-default TLS cipher list on hosts
       that deliver email to the public Internet: you will be unable to  send  email  to  servers
       that  only  support  the  ciphers  you exclude. Using a restricted cipher list may be more
       appropriate for an internal MTA, where one can exert some control over  the  TLS  software
       and settings of the peer servers.

       Note: do not use "" quotes around the parameter value.

       This  feature  is  available  in  Postfix version 2.2. It is not used with Postfix 2.3 and
       later; use smtp_tls_mandatory_ciphers instead.

smtp_tls_ciphers (default: export)
       The minimum TLS cipher grade that the Postfix SMTP client will use with opportunistic  TLS
       encryption.  Cipher  types  listed  in smtp_tls_exclude_ciphers are excluded from the base
       definition of the selected cipher grade. The default value "export" ensures maximum inter-
       operability.  Because  encryption  is optional, stronger controls are not appropriate, and
       this setting SHOULD NOT be changed unless the change is essential.

       When TLS is mandatory the cipher grade is chosen via the  smtp_tls_mandatory_ciphers  con-
       figuration  parameter, see there for syntax details. See smtp_tls_policy_maps for informa-
       tion on how to configure ciphers on a per-destination basis.

       Example:
       smtp_tls_ciphers = export

       This feature is available in Postfix 2.6 and later. With earlier Postfix releases only the
       smtp_tls_mandatory_ciphers  parameter  is  implemented,	and opportunistic TLS always uses
       "export" or better (i.e. all) ciphers.

smtp_tls_dcert_file (default: empty)
       File with the Postfix SMTP client DSA certificate in PEM format.  This file may also  con-
       tain the Postfix SMTP client private DSA key.

       See the discussion under smtp_tls_cert_file for more details.

       Example:

       smtp_tls_dcert_file = /etc/postfix/client-dsa.pem

       This feature is available in Postfix 2.2 and later.

smtp_tls_dkey_file (default: $smtp_tls_dcert_file)
       File  with  the	Postfix SMTP client DSA private key in PEM format.  This file may be com-
       bined   with   the   Postfix   SMTP   client   DSA   certificate   file	 specified   with
       $smtp_tls_dcert_file.

       The  private  key must be accessible without a pass-phrase, i.e. it must not be encrypted.
       File permissions should grant read-only access to the system superuser  account	("root"),
       and no access to anyone else.

       This feature is available in Postfix 2.2 and later.

smtp_tls_eccert_file (default: empty)
       File  with  the	Postfix  SMTP client ECDSA certificate in PEM format.  This file may also
       contain the Postfix SMTP client ECDSA private key.

       See the discussion under smtp_tls_cert_file for more details.

       Example:

       smtp_tls_eccert_file = /etc/postfix/ecdsa-ccert.pem

       This feature is available in Postfix 2.6 and later, when Postfix is  compiled  and  linked
       with OpenSSL 1.0.0 or later.

smtp_tls_eckey_file (default: $smtp_tls_eccert_file)
       File  with the Postfix SMTP client ECDSA private key in PEM format.  This file may be com-
       bined  with  the   Postfix   SMTP   client   ECDSA   certificate   file	 specified   with
       $smtp_tls_eccert_file.

       The  private  key must be accessible without a pass-phrase, i.e. it must not be encrypted.
       File permissions should grant read-only access to the system superuser  account	("root"),
       and no access to anyone else.

       This  feature  is  available in Postfix 2.6 and later, when Postfix is compiled and linked
       with OpenSSL 1.0.0 or later.

smtp_tls_enforce_peername (default: yes)
       With mandatory TLS encryption, require that the remote SMTP server  hostname  matches  the
       information  in	the  remote SMTP server certificate.  As of RFC 2487 the requirements for
       hostname checking for MTA clients are not specified.

       This option can be set to "no" to disable strict peer name checking. This setting  has  no
       effect on sessions that are controlled via the smtp_tls_per_site table.

       Disabling the hostname verification can make sense in closed environment where special CAs
       are created.  If not used carefully, this option opens the danger of a "man-in-the-middle"
       attack (the CommonName of this attacker will be logged).

       This  feature  is  available  in  Postfix  2.2  and  later. With Postfix 2.3 and later use
       smtp_tls_security_level instead.

smtp_tls_exclude_ciphers (default: empty)
       List of ciphers or cipher types to exclude from the Postfix SMTP client cipher list at all
       TLS  security  levels. This is not an OpenSSL cipherlist, it is a simple list separated by
       whitespace and/or commas. The elements are a single cipher, or one or more  "+"	separated
       cipher properties, in which case only ciphers matching all the properties are excluded.

       Examples (some of these will cause problems):

	   smtp_tls_exclude_ciphers = aNULL
	   smtp_tls_exclude_ciphers = MD5, DES
	   smtp_tls_exclude_ciphers = DES+MD5
	   smtp_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
	   smtp_tls_exclude_ciphers = kEDH+aRSA

       The  first setting, disables anonymous ciphers. The next setting disables ciphers that use
       the MD5 digest algorithm or the (single) DES encryption algorithm. The next  setting  dis-
       ables  ciphers  that  use MD5 and DES together.	The next setting disables the two ciphers
       "AES256-SHA" and "DES-CBC3-MD5". The last setting disables  ciphers  that  use  "EDH"  key
       exchange with RSA authentication.

       This feature is available in Postfix 2.3 and later.

smtp_tls_fingerprint_cert_match (default: empty)
       List  of  acceptable remote SMTP server certificate fingerprints for the "fingerprint" TLS
       security level (smtp_tls_security_level = fingerprint). At this security  level,  certifi-
       cate  authorities  are  not  used,  and certificate expiration times are ignored. Instead,
       server certificates are verified directly via their "fingerprint". The  fingerprint  is	a
       message	digest	of  the  server  certificate.  The  digest  algorithm is selected via the
       smtp_tls_fingerprint_digest parameter.

       When an smtp_tls_policy_maps table entry specifies the "fingerprint" security  level,  any
       "match"	attributes  in	that  entry specify the list of valid fingerprints for the corre-
       sponding destination. Multiple fingerprints can be combined with a "|" delimiter in a sin-
       gle match attribute, or multiple match attributes can be employed.

       Example: Certificate fingerprint verification with internal mailhub.  Two matching finger-
       prints are listed. The relayhost may be multiple physical hosts	behind	a  load-balancer,
       each  with its own private/public key and self-signed certificate. Alternatively, a single
       relayhost may be in the process of switching  from  one	set  of  private/public  keys  to
       another, and both keys are trusted just prior to the transition.

	   relayhost = [mailhub.example.com]
	   smtp_tls_security_level = fingerprint
	   smtp_tls_fingerprint_digest = md5
	   smtp_tls_fingerprint_cert_match =
	       3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
	       EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       Example: Certificate fingerprint verification with selected destinations.  As in the exam-
       ple above, we show two matching fingerprints:

	   /etc/postfix/main.cf:
	       smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
	       smtp_tls_fingerprint_digest = md5

	   /etc/postfix/tls_policy:
	       example.com     fingerprint
		   match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
		   match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       This feature is available in Postfix 2.5 and later.

smtp_tls_fingerprint_digest (default: md5)
       The message digest algorithm used to construct  remote  SMTP  server  certificate  finger-
       prints.	At  the "fingerprint" TLS security level (smtp_tls_security_level = fingerprint),
       the server certificate is verified by directly matching its fingerprint.  The  fingerprint
       is  the	message  digest  of  the  server certificate using the selected algorithm. With a
       digest algorithm resistant to "second pre-image" attacks, it is not feasible to	create	a
       new public key and a matching certificate that has the same fingerprint.

       The  default algorithm is md5; this is consistent with the backwards compatible setting of
       the digest used to verify client certificates in the SMTP server.

       The best practice algorithm is now sha1. Recent advances in  hash  function  cryptanalysis
       have led to md5 being deprecated in favor of sha1.  However, as long as there are no known
       "second pre-image" attacks against md5, its use in this context can  still  be  considered
       safe.

       While  additional  digest  algorithms  are  often available with OpenSSL's libcrypto, only
       those used by libssl in SSL cipher suites are available to Postfix.  For  now  this  means
       just md5 or sha1.

       To  find the fingerprint of a specific certificate file, with a specific digest algorithm,
       run:

	   $ openssl x509 -noout -fingerprint -digest -in certfile.pem

       The text to the right of "=" sign is the desired fingerprint.  For example:

	   $ openssl x509 -noout -fingerprint -sha1 -in cert.pem
	   SHA1 Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A

       This feature is available in Postfix 2.5 and later.

smtp_tls_key_file (default: $smtp_tls_cert_file)
       File with the Postfix SMTP client RSA private key in PEM format.  This file  may  be  com-
       bined   with   the   Postfix   SMTP   client   RSA   certificate   file	 specified   with
       $smtp_tls_cert_file.

       The private key must be accessible without a pass-phrase, i.e. it must not  be  encrypted.
       File  permissions  should grant read-only access to the system superuser account ("root"),
       and no access to anyone else.

       Example:

       smtp_tls_key_file = $smtp_tls_cert_file

       This feature is available in Postfix 2.2 and later.

smtp_tls_loglevel (default: 0)
       Enable additional Postfix SMTP client logging of TLS activity.  Each  logging  level  also
       includes the information that is logged at a lower logging level.

	      0 Disable logging of TLS activity.

	      1 Log TLS handshake and certificate information.

	      2 Log levels during TLS negotiation.

	      3 Log hexadecimal and ASCII dump of TLS negotiation process.

	      4 Log hexadecimal and ASCII dump of complete transmission after STARTTLS.

       Use  "smtp_tls_loglevel	= 3" only in case of problems. Use of loglevel 4 is strongly dis-
       couraged.

       This feature is available in Postfix 2.2 and later.

smtp_tls_mandatory_ciphers (default: medium)
       The minimum TLS cipher grade that the Postfix SMTP client  will	use  with  mandatory  TLS
       encryption.   The  default value "medium" is suitable for most destinations with which you
       may want to enforce TLS, and is beyond the reach of  today's  cryptanalytic  methods.  See
       smtp_tls_policy_maps  for  information  on  how	to configure ciphers on a per-destination
       basis.

       The following cipher grades are supported:

       export Enable "EXPORT" grade or better OpenSSL ciphers.	This is the  default  for  oppor-
	      tunistic encryption. It is not recommended for mandatory encryption unless you must
	      enforce TLS with "crippled" peers. The underlying cipherlist is specified  via  the
	      tls_export_cipherlist configuration parameter, which you are strongly encouraged to
	      not change.

       low    Enable "LOW" grade or better OpenSSL ciphers.  This setting is only appropriate for
	      internal	 mail	servers.    The   underlying  cipherlist  is  specified  via  the
	      tls_low_cipherlist configuration parameter, which you are  strongly  encouraged  to
	      not change.

       medium Enable  "MEDIUM"	grade  or  better  OpenSSL ciphers.  The underlying cipherlist is
	      specified via the tls_medium_cipherlist  configuration  parameter,  which  you  are
	      strongly encouraged to not change.

       high   Enable only "HIGH" grade OpenSSL ciphers.  This setting may be appropriate when all
	      mandatory TLS destinations (e.g. when all mail is  routed  to  a	suitably  capable
	      relayhost)  support  at least one "HIGH" grade cipher. The underlying cipherlist is
	      specified via  the  tls_high_cipherlist  configuration  parameter,  which  you  are
	      strongly encouraged to not change.

       null   Enable  only  the  "NULL"  OpenSSL  ciphers,  these  provide authentication without
	      encryption.  This setting is only appropriate in the rare case that all servers are
	      prepared	to  use  NULL  ciphers (not normally enabled in TLS servers). A plausible
	      use-case is an LMTP server listening on a UNIX-domain socket that is configured  to
	      support	"NULL"	 ciphers.   The   underlying  cipherlist  is  specified  via  the
	      tls_null_cipherlist configuration parameter, which you are strongly  encouraged  to
	      not change.

       The  underlying	cipherlists  for  grades other than "null" include anonymous ciphers, but
       these are automatically filtered out if the Postfix SMTP client is  configured  to  verify
       server certificates.  You are very unlikely to need to take any steps to exclude anonymous
       ciphers, they are excluded automatically as necessary.	If  you  must  exclude	anonymous
       ciphers	at  the "may" or "encrypt" security levels, when the Postfix SMTP client does not
       need or use peer certificates, set "smtp_tls_exclude_ciphers = aNULL". To  exclude  anony-
       mous ciphers only when TLS is enforced, set "smtp_tls_mandatory_exclude_ciphers = aNULL".

       This feature is available in Postfix 2.3 and later.

smtp_tls_mandatory_exclude_ciphers (default: empty)
       Additional  list of ciphers or cipher types to exclude from the SMTP client cipher list at
       mandatory TLS security levels. This list works in addition to the exclusions  listed  with
       smtp_tls_exclude_ciphers (see there for syntax details).

       Starting  with Postfix 2.6, the mandatory cipher exclusions can be specified on a per-des-
       tination basis via the TLS policy "exclude" attribute. See smtp_tls_policy_maps for  notes
       and examples.

       This feature is available in Postfix 2.3 and later.

smtp_tls_mandatory_protocols (default: !SSLv2)
       List of SSL/TLS protocols that the Postfix SMTP client will use with mandatory TLS encryp-
       tion.  In main.cf the values are separated by whitespace, commas or colons. In the  policy
       table  "protocols" attribute (see smtp_tls_policy_maps) the only valid separator is colon.
       An empty value means allow all protocols. The valid protocol names, (see \fBfBSSL_get_ver-
       sion(3)), are "SSLv2", "SSLv3" and "TLSv1".

       Note:  As  of  OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1" and "TLSv1.2". If an
       older Postfix version is linked against OpenSSL 1.0.1 or later, these, or  any  other  new
       protocol versions, are unconditionally enabled.

       With  Postfix  >= 2.5 the parameter syntax is expanded to support protocol exclusions. One
       can now explicitly exclude SSLv2 by setting "smtp_tls_mandatory_protocols  =  !SSLv2".  To
       exclude	both SSLv2 and SSLv3 set "smtp_tls_mandatory_protocols = !SSLv2, !SSLv3". Listing
       the protocols to include, rather than protocols to exclude, is supported, but  not  recom-
       mended.	The exclusion form more closely matches the behaviour when the OpenSSL library is
       newer than Postfix.

       Since SSL version 2 has known protocol weaknesses and is now deprecated, the default  set-
       ting  excludes "SSLv2".	This means that by default, SSL version 2 will not be used at the
       "encrypt" security level and higher.

       See the documentation of the smtp_tls_policy_maps parameter and TLS_README for more infor-
       mation about security levels.

       Example:

       # Preferred form with Postfix >= 2.5:
       smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
       # Alternative form.
       smtp_tls_mandatory_protocols = TLSv1

       This feature is available in Postfix 2.3 and later.

smtp_tls_note_starttls_offer (default: no)
       Log  the  hostname  of  a remote SMTP server that offers STARTTLS, when TLS is not already
       enabled for that server.

       The logfile record looks like:

       postfix/smtp[pid]:  Host offered STARTTLS: [name.of.host]

       This feature is available in Postfix 2.2 and later.

smtp_tls_per_site (default: empty)
       Optional lookup tables with the Postfix SMTP client TLS usage policy by next-hop  destina-
       tion  and  by  remote  SMTP server hostname.  When both lookups succeed, the more specific
       per-site policy (NONE, MUST, etc) overrides the less specific  one  (MAY),  and	the  more
       secure per-site policy (MUST, etc) overrides the less secure one (NONE).  With Postfix 2.3
       and later smtp_tls_per_site is strongly discouraged: use smtp_tls_policy_maps instead.

       Use of the bare hostname as the per-site table lookup key is discouraged. Always  use  the
       full  destination  nexthop  (enclosed  in  [] with a possible ":port" suffix). A recipient
       domain or MX-enabled transport next-hop with no port suffix may look like a bare hostname,
       but is still a suitable destination.

       Specify	a next-hop destination or server hostname on the left-hand side; no wildcards are
       allowed. The next-hop destination is either the recipient domain, or the destination spec-
       ified  with  a transport(5) table, the relayhost parameter, or the relay_transport parame-
       ter.  On the right hand side specify one of the following keywords:

       NONE   Don't use TLS at all. This overrides a less specific MAY	lookup	result	from  the
	      alternate  host  or  next-hop  lookup  key,  and overrides the global smtp_use_tls,
	      smtp_enforce_tls, and smtp_tls_enforce_peername settings.

       MAY    Try to use TLS if the server announces support, otherwise use the unencrypted  con-
	      nection. This has less precedence than a more specific result (including NONE) from
	      the alternate host or next-hop lookup key, and has less precedence  than	the  more
	      specific global "smtp_enforce_tls = yes" or "smtp_tls_enforce_peername = yes".

       MUST_NOPEERMATCH
	      Require  TLS  encryption,  but  do not require that the remote SMTP server hostname
	      matches the information in the remote SMTP server certificate, or that  the  server
	      certificate was issued by a trusted CA. This overrides a less secure NONE or a less
	      specific MAY lookup result from the alternate host  or  next-hop	lookup	key,  and
	      overrides  the  global smtp_use_tls, smtp_enforce_tls and smtp_tls_enforce_peername
	      settings.

       MUST   Require TLS encryption, require that the remote SMTP server  hostname  matches  the
	      information in the remote SMTP server certificate, and require that the remote SMTP
	      server certificate was issued by a trusted CA. This overrides a  less  secure  NONE
	      and  MUST_NOPEERMATCH  or a less specific MAY lookup result from the alternate host
	      or next-hop lookup key, and overrides the global smtp_use_tls, smtp_enforce_tls and
	      smtp_tls_enforce_peername settings.

       The above keywords correspond to the "none", "may", "encrypt" and "verify" security levels
       for the new smtp_tls_security_level parameter introduced in  Postfix  2.3.  Starting  with
       Postfix	2.3,  and  independently  of  how  the	policy	is specified, the smtp_tls_manda-
       tory_ciphers and smtp_tls_mandatory_protocols parameters  apply	when  TLS  encryption  is
       mandatory.  Connections	for  which  encryption	is optional typically enable all "export"
       grade and better ciphers (see smtp_tls_ciphers and smtp_tls_protocols).

       As long as no secure DNS lookup mechanism is available, false hostnames	in  MX	or  CNAME
       responses  can  change  the  server  hostname  that Postfix uses for TLS policy lookup and
       server certificate verification. Even with a perfect match between the server hostname and
       the  server  certificate,  there  is  no  guarantee that Postfix is connected to the right
       server.	See TLS_README (Closing a DNS loophole with obsolete per-site TLS policies) for a
       possible work-around.

       This  feature  is  available  in  Postfix  2.2  and  later. With Postfix 2.3 and later use
       smtp_tls_policy_maps instead.

smtp_tls_policy_maps (default: empty)
       Optional lookup tables with the Postfix SMTP client TLS security policy by next-hop desti-
       nation; when a non-empty value is specified, this overrides the obsolete smtp_tls_per_site
       parameter.  See TLS_README for a more detailed discussion of TLS security levels.

       The TLS policy table is indexed by the full next-hop  destination,  which  is  either  the
       recipient domain, or the verbatim next-hop specified in the transport table, $local_trans-
       port,  $virtual_transport,  $relay_transport  or  $default_transport.  This  includes  any
       enclosing  square  brackets  and  any non-default destination server port suffix. The LMTP
       socket type prefix (inet: or unix:) is not included in the lookup key.

       Only the next-hop domain, or $myhostname with LMTP over UNIX-domain sockets,  is  used  as
       the  nexthop name for certificate verification. The port and any enclosing square brackets
       are used in the table lookup key, but are not used for server name verification.

       When the lookup key is a domain name without enclosing square brackets or any :port suffix
       (typically  the	recipient domain), and the full domain is not found in the table, just as
       with the transport(5) table, the parent domain starting with  a	leading  "."  is  matched
       recursively.  This  allows one to specify a security policy for a recipient domain and all
       its sub-domains.

       The lookup result is a security level, followed by an optional list of  whitespace  and/or
       comma  separated  name=value  attributes  that  override related main.cf settings. The TLS
       security levels in order of increasing security are:

       none   No TLS. No additional attributes are supported at this level.

       may    Opportunistic TLS. Since sending in the clear  is  acceptable,  demanding  stronger
	      than default TLS security merely reduces inter-operability. The optional "ciphers",
	      "exclude" and "protocols" attributes (available for opportunistic TLS with  Postfix
	      >=   2.6)   override   the   "smtp_tls_ciphers",	 "smtp_tls_exclude_ciphers"   and
	      "smtp_tls_protocols" configuration parameters. When  opportunistic  TLS  handshakes
	      fail,  Postfix retries the connection with TLS disabled.	This allows mail delivery
	      to sites with non-interoperable TLS implementations.

       encrypt
	      Mandatory TLS encryption. At  this  level  and  higher,  the  optional  "protocols"
	      attribute   overrides   the  main.cf  smtp_tls_mandatory_protocols  parameter,  the
	      optional	"ciphers"  attribute  overrides  the  main.cf  smtp_tls_mandatory_ciphers
	      parameter,  and  the  optional  "exclude"  attribute (Postfix >= 2.6) overrides the
	      main.cf smtp_tls_mandatory_exclude_ciphers parameter. In the policy table, multiple
	      protocols  or excluded ciphers must be separated by colons, as attribute values may
	      not contain whitespace or commas.

       fingerprint
	      Certificate fingerprint verification. Available with Postfix 2.5 and later. At this
	      security level, there are no trusted certificate authorities. The certificate trust
	      chain, expiration date, ... are not checked. Instead, the optional match attribute,
	      or  else	the  main.cf  smtp_tls_fingerprint_cert_match  parameter, lists the valid
	      "fingerprints" of the server certificate. The digest algorithm  used  to	calculate
	      the  fingerprint is selected by the smtp_tls_fingerprint_digest parameter. Multiple
	      fingerprints can be combined with a "|" delimiter in a single match  attribute,  or
	      multiple	match  attributes  can	be  employed.  The ":" character is not used as a
	      delimiter as it occurs between each pair of fingerprint (hexadecimal) digits.

       verify Mandatory TLS verification.  At this security level, DNS MX lookups are trusted  to
	      be  secure  enough,  and	the  name  verified  in the server certificate is usually
	      obtained indirectly via unauthenticated  DNS  MX	lookups.   The	optional  "match"
	      attribute overrides the main.cf smtp_tls_verify_cert_match parameter. In the policy
	      table, multiple match patterns and strategies must  be  separated  by  colons.   In
	      practice	explicit  control  over matching is more common with the "secure" policy,
	      described below.

       secure Secure-channel TLS. At this security level, DNS MX lookups, though potentially used
	      to  determine  the  candidate  next-hop gateway IP addresses, are not trusted to be
	      secure enough for TLS peername verification. Instead, the default name verified  in
	      the  server  certificate	is  obtained directly from the next-hop, or is explicitly
	      specified  via  the  optional  match  attribute	which	overrides   the   main.cf
	      smtp_tls_secure_cert_match  parameter. In the policy table, multiple match patterns
	      and strategies must be separated by colons.  The match  attribute  is  most  useful
	      when  multiple domains are supported by common server, the policy entries for addi-
	      tional domains specify matching rules for the  primary  domain  certificate.  While
	      transport table overrides routing the secondary domains to the primary nexthop also
	      allow secure verification, they risk delivery to the wrong destination when domains
	      change  hands  or  are  re-assigned  to  new  gateways.  With the "match" attribute
	      approach, routing is not perturbed, and mail is deferred if verification of  a  new
	      MX host fails.

       Example:

       /etc/postfix/main.cf:
	   smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
	   # Postfix 2.5 and later
	   smtp_tls_fingerprint_digest = md5

       /etc/postfix/tls_policy:
	   example.edu		       none
	   example.mil		       may
	   example.gov		       encrypt protocols=TLSv1
	   example.com		       verify ciphers=high
	   example.net		       secure
	   .example.net 	       secure match=.example.net:example.net
	   [mail.example.org]:587      secure match=nexthop
	   # Postfix 2.5 and later
	   [thumb.example.org]		fingerprint
	    match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
	    match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1

       Note:	The    hostname    strategy    if    listed   in   a   non-default   setting   of
       smtp_tls_secure_cert_match or in the match attribute in the policy table  can  render  the
       secure  level vulnerable to DNS forgery. Do not use the hostname strategy for secure-chan-
       nel configurations in environments where DNS security is not assured.

       This feature is available in Postfix 2.3 and later.

smtp_tls_protocols (default: !SSLv2)
       List of TLS protocols that the Postfix SMTP client will exclude	or  include  with  oppor-
       tunistic  TLS  encryption.  Starting  with  Postfix  2.6,  the Postfix SMTP client will by
       default not use the obsolete SSLv2 protocol.

       In main.cf the values are separated by whitespace, commas or colons. In the  policy  table
       (see  smtp_tls_policy_maps)  the only valid separator is colon. An empty value means allow
       all protocols. The valid  protocol  names,  (see  \fBfBSSL_get_version(3)),  are  "SSLv2",
       "SSLv3" and "TLSv1".

       Note:  As  of  OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1" and "TLSv1.2". If an
       older Postfix version is linked against OpenSSL 1.0.1 or later, these, or  any  other  new
       protocol versions, are unconditionally enabled.

       To  include a protocol list its name, to exclude it, prefix the name with a "!" character.
       To exclude SSLv2 even for opportunistic TLS set "smtp_tls_protocols = !SSLv2". To  exclude
       both "SSLv2" and "SSLv3" set "smtp_tls_protocols = !SSLv2, !SSLv3". Explicitly listing the
       protocols to include, rather than protocols to exclude, is supported, but not recommended.
       The  exclusion  form  more closely matches the behaviour when the OpenSSL library is newer
       than Postfix.

       Example:
       # TLSv1 only!
       smtp_tls_protocols = !SSLv2, !SSLv3

       This feature is available in Postfix 2.6 and later.

smtp_tls_scert_verifydepth (default: 9)
       The verification depth for remote SMTP server certificates. A depth of 1 is sufficient  if
       the issuing CA is listed in a local CA file.

       The  default  verification depth is 9 (the OpenSSL default) for compatibility with earlier
       Postfix behavior. Prior to Postfix 2.5, the default value was 5, but  the  limit  was  not
       actually  enforced.  If	you have set this to a lower non-default value, certificates with
       longer trust chains may now fail to verify. Certificate chains with 1 or 2 CAs are common,
       deeper chains are more rare and any number between 5 and 9 should suffice in practice. You
       can choose a lower number if, for example, you trust certificates directly  signed  by  an
       issuing CA but not any CAs it delegates to.

       This feature is available in Postfix 2.2 and later.

smtp_tls_secure_cert_match (default: nexthop, dot-nexthop)
       The  server  certificate peername verification method for the "secure" TLS security level.
       In a  "secure"  TLS  policy  table  ($smtp_tls_policy_maps)  entry  the	optional  "match"
       attribute overrides this main.cf setting.

       This  parameter	specifies  one or more patterns or strategies separated by commas, white-
       space or colons.  In the policy table the only valid separator is the colon character.

       For a description of the pattern and strategy syntax  see  the  smtp_tls_verify_cert_match
       parameter. The "hostname" strategy should be avoided in this context, as in the absence of
       a secure global DNS, using the results of MX lookups in certificate  verification  is  not
       immune to active (man-in-the-middle) attacks on DNS.

       Sample main.cf setting:

	   smtp_tls_secure_cert_match = nexthop

       Sample policy table override:

	   example.net	   secure match=example.com:.example.com
	   .example.net    secure match=example.com:.example.com

       This feature is available in Postfix 2.3 and later.

smtp_tls_security_level (default: empty)
       The default SMTP TLS security level for the Postfix SMTP client; when a non-empty value is
       specified, this overrides the  obsolete	parameters  smtp_use_tls,  smtp_enforce_tls,  and
       smtp_tls_enforce_peername.

       Specify one of the following security levels:

       none   TLS  will  not  be  used unless enabled for specific destinations via smtp_tls_pol-
	      icy_maps.

       may    Opportunistic TLS. Use TLS if this is supported by the remote SMTP  server,  other-
	      wise  use  plaintext.  Since sending in the clear is acceptable, demanding stronger
	      than default TLS security merely reduces inter-operability.  The "smtp_tls_ciphers"
	      and  "smtp_tls_protocols" (Postfix >= 2.6) configuration parameters provide control
	      over the protocols and cipher grade used	with  opportunistic  TLS.   With  earlier
	      releases the opportunistic TLS cipher grade is always "export" and no protocols are
	      disabled.  When TLS handshakes fail, the connection is retried with  TLS	disabled.
	      This allows mail delivery to sites with non-interoperable TLS implementations.

       encrypt
	      Mandatory TLS encryption. Since a minimum level of security is intended, it is rea-
	      sonable to be specific about sufficiently secure protocol versions and ciphers.  At
	      this security level and higher, the main.cf parameters smtp_tls_mandatory_protocols
	      and smtp_tls_mandatory_ciphers specify the TLS protocols and minimum  cipher  grade
	      which  the  administrator considers secure enough for mandatory encrypted sessions.
	      This security level is not an appropriate default for systems  delivering  mail  to
	      the Internet.

       fingerprint
	      Certificate fingerprint verification. Available with Postfix 2.5 and later. At this
	      security level, there are no trusted certificate authorities. The certificate trust
	      chain,  expiration  date,  ...  are  not	checked.  Instead,  the  smtp_tls_finger-
	      print_cert_match parameter lists the valid "fingerprints" of  the  server  certifi-
	      cate.  The  digest  algorithm  used to calculate the fingerprint is selected by the
	      smtp_tls_fingerprint_digest parameter.

       verify Mandatory TLS verification. At this security level, DNS MX lookups are  trusted  to
	      be  secure  enough,  and	the  name  verified  in the server certificate is usually
	      obtained	indirectly  via  unauthenticated  DNS  MX  lookups.   The   smtp_tls_ver-
	      ify_cert_match  parameter  controls  how	the  server name is verified. In practice
	      explicit control over matching is more common  at  the  "secure"	level,	described
	      below.  This  security  level  is not an appropriate default for systems delivering
	      mail to the Internet.

       secure Secure-channel TLS.  At this security level, DNS	MX  lookups,  though  potentially
	      used  to	determine the candidate next-hop gateway IP addresses, are not trusted to
	      be secure enough for TLS peername verification. Instead, the default name  verified
	      in  the server certificate is obtained from the next-hop domain as specified in the
	      smtp_tls_secure_cert_match configuration parameter. The default  matching  rule  is
	      that  a  server certificate matches when its name is equal to or is a sub-domain of
	      the nexthop domain. This security level is not an appropriate default  for  systems
	      delivering mail to the Internet.

       Examples:

       # No TLS. Formerly: smtp_use_tls=no and smtp_enforce_tls=no.
       smtp_tls_security_level = none

       # Opportunistic TLS.
       smtp_tls_security_level = may
       # Postfix >= 2.6:
       # Do not tweak opportunistic ciphers or protocol unless it is essential
       # to do so (if a security vulnerability is found in the SSL library that
       # can be mitigated by disabling a particular protocol or raising the
       # cipher grade from "export" to "low" or "medium").
       smtp_tls_ciphers = export
       smtp_tls_protocols = !SSLv2

       # Mandatory (high-grade) TLS encryption.
       smtp_tls_security_level = encrypt
       smtp_tls_mandatory_ciphers = high

       # Mandatory TLS verification of hostname or nexthop domain.
       smtp_tls_security_level = verify
       smtp_tls_mandatory_ciphers = high
       smtp_tls_verify_cert_match = hostname, nexthop, dot-nexthop

       # Secure channel TLS with exact nexthop name match.
       smtp_tls_security_level = secure
       smtp_tls_mandatory_protocols = TLSv1
       smtp_tls_mandatory_ciphers = high
       smtp_tls_secure_cert_match = nexthop

       # Certificate fingerprint verification (Postfix >= 2.5).
       # The CA-less "fingerprint" security level only scales to a limited
       # number of destinations. As a global default rather than a per-site
       # setting, this is practical when mail for all recipients is sent
       # to a central mail hub.
       relayhost = [mailhub.example.com]
       smtp_tls_security_level = fingerprint
       smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
       smtp_tls_mandatory_ciphers = high
       smtp_tls_fingerprint_cert_match =
	   3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
	   EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       This feature is available in Postfix 2.3 and later.

smtp_tls_session_cache_database (default: empty)
       Name  of the file containing the optional Postfix SMTP client TLS session cache. Specify a
       database type that supports enumeration, such as btree or sdbm; there is no need  to  sup-
       port concurrent access.	The file is created if it does not exist. The smtp(8) daemon does
       not use this parameter directly,  rather  the  cache  is  implemented  indirectly  in  the
       tlsmgr(8)  daemon. This means that per-smtp-instance master.cf overrides of this parameter
       are not effective.  Note, that each of the cache databases supported by tlsmgr(8)  daemon:
       $smtpd_tls_session_cache_database,  $smtp_tls_session_cache_database (and with Postfix 2.3
       and later $lmtp_tls_session_cache_database), needs to be stored separately. It is  not  at
       this time possible to store multiple caches in a single database.

       Note: dbm databases are not suitable. TLS session objects are too large.

       As of version 2.5, Postfix no longer uses root privileges when opening this file. The file
       should now be stored under the  Postfix-owned  data_directory.  As  a  migration  aid,  an
       attempt	to open the file under a non-Postfix directory is redirected to the Postfix-owned
       data_directory, and a warning is logged.

       Example:

       smtp_tls_session_cache_database = btree:/var/db/postfix/smtp_scache

       This feature is available in Postfix 2.2 and later.

smtp_tls_session_cache_timeout (default: 3600s)
       The expiration time of Postfix SMTP client TLS session cache information.  A cache cleanup
       is   performed	periodically   every  $smtp_tls_session_cache_timeout  seconds.  As  with
       $smtp_tls_session_cache_database, this parameter is implemented in  the	tlsmgr(8)  daemon
       and therefore per-smtp-instance master.cf overrides are not possible.

       This feature is available in Postfix 2.2 and later.

smtp_tls_verify_cert_match (default: hostname)
       The  server  certificate peername verification method for the "verify" TLS security level.
       In a  "verify"  TLS  policy  table  ($smtp_tls_policy_maps)  entry  the	optional  "match"
       attribute overrides this main.cf setting.

       This  parameter	specifies  one or more patterns or strategies separated by commas, white-
       space or colons.  In the policy table the only valid separator is the colon character.

       Patterns specify domain names, or domain name suffixes:

       example.com
	      Match the example.com domain, i.e. one of the names the server certificate must  be
	      example.com, upper and lower case distinctions are ignored.

       .example.com
	      Match  subdomains  of  the example.com domain, i.e. match a name in the server cer-
	      tificate that consists of a non-zero number of labels followed  by  a  .example.com
	      suffix. Case distinctions are ignored.

       Strategies  specify  a transformation from the next-hop domain to the expected name in the
       server certificate:

       nexthop
	      Match against the next-hop domain, which is either the  recipient  domain,  or  the
	      transport  next-hop  configured for the domain stripped of any optional socket type
	      prefix, enclosing square brackets and trailing port. When MX lookups are	not  sup-
	      pressed, this is the original nexthop domain prior to the MX lookup, not the result
	      of the MX lookup. For LMTP delivery via UNIX-domain sockets, the verified  next-hop
	      name  is	$myhostname.  This strategy is suitable for use with the "secure" policy.
	      Case is ignored.

       dot-nexthop
	      As above, but match server certificate names that are subdomains	of  the  next-hop
	      domain. Case is ignored.

       hostname
	      Match against the hostname of the server, often obtained via an unauthenticated DNS
	      MX lookup. For LMTP delivery via UNIX-domain sockets, the verified name is $myhost-
	      name.  This matches the verification strategy of the "MUST" keyword in the obsolete
	      smtp_tls_per_site table, and is suitable for use with the "verify" security  level.
	      When  the  next-hop name is enclosed in square brackets to suppress MX lookups, the
	      "hostname" strategy is the same as the "nexthop" strategy. Case is ignored.

       Sample main.cf setting:

       smtp_tls_verify_cert_match = hostname, nexthop, dot-nexthop

       Sample policy table override:

       example.com     verify  match=hostname:nexthop
       .example.com    verify  match=example.com:.example.com:hostname

       This feature is available in Postfix 2.3 and later.

smtp_use_tls (default: no)
       Opportunistic mode: use TLS when a remote SMTP server announces STARTTLS  support,  other-
       wise  send  the	mail in the clear. Beware: some SMTP servers offer STARTTLS even if it is
       not configured.	With Postfix < 2.3, if the TLS handshake fails, and no	other  server  is
       available, delivery is deferred and mail stays in the queue. If this is a concern for you,
       use the smtp_tls_per_site feature instead.

       This feature is available in Postfix 2.2  and  later.  With  Postfix  2.3  and  later  use
       smtp_tls_security_level instead.

smtp_xforward_timeout (default: 300s)
       The  SMTP client time limit for sending the XFORWARD command, and for receiving the server
       response.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1 and later.

smtpd_authorized_verp_clients (default: $authorized_verp_clients)
       What  SMTP  clients  are allowed to specify the XVERP command.  This command requests that
       mail be delivered one recipient at a time with a per recipient return address.

       By default, no clients are allowed to specify XVERP.

       This parameter was renamed with Postfix version 2.1. The default value is  backwards  com-
       patible with Postfix version 2.0.

       Specify	a  list  of  network/netmask patterns, separated by commas and/or whitespace. The
       mask specifies the number of bits in the network part of a  host  address.  You	can  also
       specify	hostnames  or  .domain names (the initial dot causes the domain to match any name
       below it),  "/file/name" or "type:table" patterns.  A "/file/name" pattern is replaced  by
       its  contents;  a "type:table" lookup table is matched when a table entry matches a lookup
       string (the lookup result is ignored).  Continue long lines by starting the next line with
       whitespace.  Specify  "!pattern" to exclude an address or network block from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note: IP version 6 address information must be specified inside	[]  in	the  smtpd_autho-
       rized_verp_clients  value,  and	in  files  specified  with  "/file/name".   IP	version 6
       addresses contain the ":" character, and would otherwise be confused with  a  "type:table"
       pattern.

smtpd_authorized_xclient_hosts (default: empty)
       What  SMTP  clients  are  allowed to use the XCLIENT feature.  This command overrides SMTP
       client information that is used for access control. Typical use is for SMTP-based  content
       filters,   fetchmail-like   programs,   or  SMTP  server  access  rule  testing.  See  the
       XCLIENT_README document for details.

       This feature is available in Postfix 2.1 and later.

       By default, no clients are allowed to specify XCLIENT.

       Specify a list of network/netmask patterns, separated by  commas  and/or  whitespace.  The
       mask  specifies	the  number  of  bits in the network part of a host address. You can also
       specify hostnames or .domain names (the initial dot causes the domain to  match	any  name
       below  it),  "/file/name" or "type:table" patterns.  A "/file/name" pattern is replaced by
       its contents; a "type:table" lookup table is matched when a table entry matches	a  lookup
       string (the lookup result is ignored).  Continue long lines by starting the next line with
       whitespace. Specify "!pattern" to exclude an address or network block from the  list.  The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version  6  address information must be specified inside [] in the smtpd_autho-
       rized_xclient_hosts value, and  in  files  specified  with  "/file/name".   IP  version	6
       addresses  contain  the ":" character, and would otherwise be confused with a "type:table"
       pattern.

smtpd_authorized_xforward_hosts (default: empty)
       What SMTP clients are allowed to use the XFORWARD feature.  This command forwards informa-
       tion  that  is  used  to  improve  logging after SMTP-based content filters. See the XFOR-
       WARD_README document for details.

       This feature is available in Postfix 2.1 and later.

       By default, no clients are allowed to specify XFORWARD.

       Specify a list of network/netmask patterns, separated by  commas  and/or  whitespace.  The
       mask  specifies	the  number  of  bits in the network part of a host address. You can also
       specify hostnames or .domain names (the initial dot causes the domain to  match	any  name
       below  it),  "/file/name" or "type:table" patterns.  A "/file/name" pattern is replaced by
       its contents; a "type:table" lookup table is matched when a table entry matches	a  lookup
       string (the lookup result is ignored).  Continue long lines by starting the next line with
       whitespace. Specify "!pattern" to exclude an address or network block from the  list.  The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version  6  address information must be specified inside [] in the smtpd_autho-
       rized_xforward_hosts value, and in  files  specified  with  "/file/name".   IP  version	6
       addresses  contain  the ":" character, and would otherwise be confused with a "type:table"
       pattern.

smtpd_banner (default: $myhostname ESMTP $mail_name)
       The text that follows the 220 status code in the SMTP greeting banner. Some people like to
       see the mail version advertised. By default, Postfix shows no version.

       You MUST specify $myhostname at the start of the text. This is required by the SMTP proto-
       col.

       Example:

       smtpd_banner = $myhostname ESMTP $mail_name ($mail_version)

smtpd_client_connection_count_limit (default: 50)
       How many simultaneous connections any client is allowed	to  make  to  this  service.   By
       default, the limit is set to half the default process limit value.

       To disable this feature, specify a limit of 0.

       WARNING:  The  purpose  of this feature is to limit abuse. It must not be used to regulate
       legitimate mail traffic.

       This feature is available in Postfix 2.2 and later.

smtpd_client_connection_rate_limit (default: 0)
       The maximal number of connection attempts any client is allowed to make	to  this  service
       per  time  unit.   The  time unit is specified with the anvil_rate_time_unit configuration
       parameter.

       By default, a client can make as many connections per time unit as Postfix can accept.

       To disable this feature, specify a limit of 0.

       WARNING: The purpose of this feature is to limit abuse. It must not be  used  to  regulate
       legitimate mail traffic.

       This feature is available in Postfix 2.2 and later.

       Example:

       smtpd_client_connection_rate_limit = 1000

smtpd_client_event_limit_exceptions (default: $mynetworks)
       Clients	that  are  excluded  from  smtpd_client_*_count/rate_limit  restrictions. See the
       mynetworks parameter description for the parameter value syntax.

       By default, clients in trusted networks are excluded. Specify a list  of  network  blocks,
       hostnames or .domain names (the initial dot causes the domain to match any name below it).

       Note:   IP   version   6   address   information  must  be  specified  inside  []  in  the
       smtpd_client_event_limit_exceptions value, and in files specified with  "/file/name".   IP
       version	6  addresses  contain  the  ":" character, and would otherwise be confused with a
       "type:table" pattern.

       This feature is available in Postfix 2.2 and later.

smtpd_client_message_rate_limit (default: 0)
       The maximal number of message delivery requests that any client is allowed to make to this
       service	per  time  unit, regardless of whether or not Postfix actually accepts those mes-
       sages.  The time unit is specified with the anvil_rate_time_unit configuration parameter.

       By default, a client can send as many message delivery requests per time unit  as  Postfix
       can accept.

       To disable this feature, specify a limit of 0.

       WARNING:  The  purpose  of this feature is to limit abuse. It must not be used to regulate
       legitimate mail traffic.

       This feature is available in Postfix 2.2 and later.

       Example:

       smtpd_client_message_rate_limit = 1000

smtpd_client_new_tls_session_rate_limit (default: 0)
       The maximal number of new (i.e., uncached) TLS sessions	that  a  remote  SMTP  client  is
       allowed to negotiate with this service per time unit.  The time unit is specified with the
       anvil_rate_time_unit configuration parameter.

       By default, a remote SMTP client can negotiate as many new TLS sessions per time  unit  as
       Postfix can accept.

       To disable this feature, specify a limit of 0. Otherwise, specify a limit that is at least
       the per-client concurrent session  limit,  or  else  legitimate	client	sessions  may  be
       rejected.

       WARNING:  The  purpose  of this feature is to limit abuse. It must not be used to regulate
       legitimate mail traffic.

       This feature is available in Postfix 2.3 and later.

       Example:

       smtpd_client_new_tls_session_rate_limit = 100

smtpd_client_port_logging (default: no)
       Enable logging of the remote SMTP client port in addition to the hostname and IP  address.
       The logging format is "host[address]:port".

       This feature is available in Postfix 2.5 and later.

smtpd_client_recipient_rate_limit (default: 0)
       The  maximal number of recipient addresses that any client is allowed to send to this ser-
       vice per time unit, regardless of whether or not Postfix actually  accepts  those  recipi-
       ents.  The time unit is specified with the anvil_rate_time_unit configuration parameter.

       By  default,  a	client	can send as many recipient addresses per time unit as Postfix can
       accept.

       To disable this feature, specify a limit of 0.

       WARNING: The purpose of this feature is to limit abuse. It must not be  used  to  regulate
       legitimate mail traffic.

       This feature is available in Postfix 2.2 and later.

       Example:

       smtpd_client_recipient_rate_limit = 1000

smtpd_client_restrictions (default: empty)
       Optional  SMTP  server  access  restrictions  in  the  context of a client SMTP connection
       request.  See SMTPD_ACCESS_README, section "Delayed evaluation of SMTP access  restriction
       lists" for a discussion of evaluation context and time.

       The default is to allow all connection requests.

       Specify	a  list  of  restrictions,  separated by commas and/or whitespace.  Continue long
       lines by starting the next line with whitespace.  Restrictions are applied in the order as
       specified; the first restriction that matches wins.

       The  following  restrictions  are  specific  to	client hostname or client network address
       information.

       check_ccert_access type:table
	      Use the client certificate fingerprint as lookup key for	the  specified	access(5)
	      database;  with  Postfix version 2.2, also require that the SMTP client certificate
	      is verified successfully.  The fingerprint digest algorithm is configurable via the
	      smtpd_tls_fingerprint_digest  parameter (hard-coded as md5 prior to Postfix version
	      2.5).  This feature is available with Postfix version 2.2 and later.

       check_client_access type:table
	      Search the specified access database  for  the  client  hostname,  parent  domains,
	      client  IP address, or networks obtained by stripping least significant octets. See
	      the access(5) manual page for details.

       check_client_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the	client	hostname,
	      and  execute  the  corresponding action.	Note: a result of "OK" is not allowed for
	      safety reasons. Instead, use DUNNO in order to exclude specific hosts  from  black-
	      lists.  This feature is available in Postfix 2.7 and later.

       check_client_ns_access type:table
	      Search  the  specified  access(5) database for the DNS servers for the client host-
	      name, and execute the corresponding action.  Note: a result of "OK" is not  allowed
	      for  safety  reasons.  Instead,  use  DUNNO in order to exclude specific hosts from
	      blacklists.  This feature is available in Postfix 2.7 and later.

       check_reverse_client_hostname_access type:table
	      Search the specified access database for the unverified  reverse	client	hostname,
	      parent domains, client IP address, or networks obtained by stripping least signifi-
	      cant octets. See the access(5) manual page for details.  Note: a result of "OK"  is
	      not  allowed  for  safety reasons.  Instead, use DUNNO in order to exclude specific
	      hosts from blacklists.  This feature is available in Postfix 2.6 and later.

       check_reverse_client_hostname_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the unverified reverse
	      client  hostname,  and execute the corresponding action.	Note: a result of "OK" is
	      not allowed for safety reasons.  Instead, use DUNNO in order  to	exclude  specific
	      hosts from blacklists.  This feature is available in Postfix 2.7 and later.

       check_reverse_client_hostname_ns_access type:table
	      Search  the  specified  access(5)  database  for the DNS servers for the unverified
	      reverse client hostname, and execute the corresponding action.  Note: a  result  of
	      "OK"  is	not  allowed  for safety reasons.  Instead, use DUNNO in order to exclude
	      specific hosts from blacklists.  This feature  is  available  in	Postfix  2.7  and
	      later.

       permit_inet_interfaces
	      Permit the request when the client IP address matches $inet_interfaces.

       permit_mynetworks
	      Permit  the  request  when  the  client  IP  address matches any network or network
	      address listed in  $mynetworks.

       permit_sasl_authenticated
	      Permit the request when the client is successfully authenticated via the	RFC  4954
	      (AUTH) protocol.

       permit_tls_all_clientcerts
	      Permit  the  request  when  the remote SMTP client certificate is verified success-
	      fully.  This option must be used only if a special CA issues the	certificates  and
	      only  this  CA  is listed as trusted CA. Otherwise, clients with a third-party cer-
	      tificate would also be allowed to relay.	Specify "tls_append_default_CA = no" when
	      the  trusted  CA is specified with smtpd_tls_CAfile or smtpd_tls_CApath, to prevent
	      Postfix from appending the system-supplied default CAs.  This feature is	available
	      with Postfix version 2.2.

       permit_tls_clientcerts
	      Permit the request when the remote SMTP client certificate fingerprint is listed in
	      $relay_clientcerts.  The fingerprint  digest  algorithm  is  configurable  via  the
	      smtpd_tls_fingerprint_digest  parameter (hard-coded as md5 prior to Postfix version
	      2.5).  This feature is available with Postfix version 2.2.

       reject_rbl_client rbl_domain=d.d.d.d
	      Reject the request when the reversed client network address is listed  with  the	A
	      record  "d.d.d.d"  under rbl_domain (Postfix version 2.1 and later only).  Each "d"
	      is a number, or a pattern inside "[]" that contains one or more ";"-separated  num-
	      bers or number..number ranges (Postfix version 2.8 and later).  If no "=d.d.d.d" is
	      specified, reject the request when the reversed client network  address  is  listed
	      with any A record under rbl_domain.
	      The  maps_rbl_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests (default:  554), the default_rbl_reply  parameter  specifies  the  default
	      server  reply,  and  the	rbl_reply_maps	 parameter  specifies  tables with server
	      replies indexed by rbl_domain.  This feature is available in Postfix 2.0 and later.

       permit_dnswl_client dnswl_domain=d.d.d.d
	      Accept the request when the reversed client network address is listed  with  the	A
	      record  "d.d.d.d"  under	dnswl_domain.	Each "d" is a number, or a pattern inside
	      "[]" that contains one or more ";"-separated numbers or number..number ranges.   If
	      no  "=d.d.d.d"  is  specified,  accept the request when the reversed client network
	      address is listed with any A record under dnswl_domain.
	      For  safety,  permit_dnswl_client  is  silently  ignored	when  it  would  override
	      reject_unauth_destination.   The	result	is  DEFER_IF_REJECT when whitelist lookup
	      fails.  This feature is available in Postfix 2.8 and later.

       reject_rhsbl_client rbl_domain=d.d.d.d
	      Reject the request when the client hostname is listed with the A	record	"d.d.d.d"
	      under  rbl_domain (Postfix version 2.1 and later only).  Each "d" is a number, or a
	      pattern inside "[]" that contains one or more ";"-separated numbers or number..num-
	      ber  ranges (Postfix version 2.8 and later).  If no "=d.d.d.d" is specified, reject
	      the request when the client hostname is listed with any A record under  rbl_domain.
	      See  the	reject_rbl_client description above for additional RBL related configura-
	      tion parameters.	This feature is available in Postfix 2.0 and later; with  Postfix
	      version  2.8  and  later,  reject_rhsbl_reverse_client  will usually produce better
	      results.

       permit_rhswl_client rhswl_domain=d.d.d.d
	      Accept the request when the client hostname is listed with the A	record	"d.d.d.d"
	      under  rhswl_domain.   Each "d" is a number, or a pattern inside "[]" that contains
	      one or more ";"-separated numbers or number..number ranges.  If  no  "=d.d.d.d"  is
	      specified,  accept the request when the client hostname is listed with any A record
	      under rhswl_domain.
	      Caution: client name whitelisting is fragile, since the client name lookup can fail
	      due  to  temporary outages.  Client name whitelisting should be used only to reduce
	      false positives in e.g.  DNS-based blocklists,  and  not	for  making  access  rule
	      exceptions.
	      For  safety,  permit_rhswl_client  is  silently  ignored	when  it  would  override
	      reject_unauth_destination.  The result is  DEFER_IF_REJECT  when	whitelist  lookup
	      fails.  This feature is available in Postfix 2.8 and later.

       reject_rhsbl_reverse_client rbl_domain=d.d.d.d
	      Reject the request when the unverified reverse client hostname is listed with the A
	      record "d.d.d.d" under rbl_domain.  Each "d" is a number, or a pattern inside  "[]"
	      that  contains  one  or more ";"-separated numbers or number..number ranges.  If no
	      "=d.d.d.d" is specified, reject the request  when  the  unverified  reverse  client
	      hostname	is  listed  with any A record under rbl_domain. See the reject_rbl_client
	      description above for additional RBL related configuration parameters.   This  fea-
	      ture is available in Postfix 2.8 and later.

       reject_unknown_client_hostname (with Postfix < 2.3: reject_unknown_client)
	      Reject  the  request  when  1)  the  client  IP address->name mapping fails, 2) the
	      name->address mapping fails, or 3) the name->address mapping  does  not  match  the
	      client IP address.
	      This is a stronger restriction than the reject_unknown_reverse_client_hostname fea-
	      ture, which triggers only under condition 1) above.
	      The unknown_client_reject_code parameter specifies the response code  for  rejected
	      requests	(default:  450).  The  reply  is  always 450 in case the address->name or
	      name->address lookup failed due to a temporary problem.

       reject_unknown_reverse_client_hostname
	      Reject the request when the client IP address has no address->name mapping.
	      This is a weaker restriction than the reject_unknown_client_hostname feature, which
	      requires not only that the address->name and name->address mappings exist, but also
	      that the two mappings reproduce the client IP address.
	      The unknown_client_reject_code parameter specifies the response code  for  rejected
	      requests	(default: 450).  The reply is always 450 in case the address->name lookup
	      failed due to a temporary problem.
	      This feature is available in Postfix 2.3 and later.

       In addition, you can use any of the following generic  restrictions.   These  restrictions
       are applicable in any SMTP command context.

       check_policy_service servername
	      Query  the  specified  policy  server.  See  the	SMTPD_POLICY_README  document for
	      details. This feature is available in Postfix 2.1 and later.

       defer  Defer the request. The client is told to try again later. This restriction is  use-
	      ful at the end of a restriction list, to make the default policy explicit.
	      The defer_code parameter specifies the SMTP server reply code (default: 450).

       defer_if_permit
	      Defer the request if some later restriction would result in an explicit or implicit
	      PERMIT action.  This is useful when a blacklisting feature fails due to a temporary
	      problem.	This feature is available in Postfix version 2.1 and later.

       defer_if_reject
	      Defer  the request if some later restriction would result in a REJECT action.  This
	      is useful when a whitelisting feature fails due to a temporary problem.  This  fea-
	      ture is available in Postfix version 2.1 and later.

       permit Permit the request. This restriction is useful at the end of a restriction list, to
	      make the default policy explicit.

       reject_multi_recipient_bounce
	      Reject the request when the envelope sender is the null address,	and  the  message
	      has  multiple envelope recipients. This usage has rare but legitimate applications:
	      under certain conditions, multi-recipient mail that was posted with the DSN  option
	      NOTIFY=NEVER may be forwarded with the null sender address.
	      Note:  this restriction can only work reliably when used in smtpd_data_restrictions
	      or smtpd_end_of_data_restrictions, because the total number of  recipients  is  not
	      known  at  an  earlier  stage of the SMTP conversation.  Use at the RCPT stage will
	      only reject the second etc.  recipient.
	      The multi_recipient_bounce_reject_code parameter specifies the  response	code  for
	      rejected	requests  (default:   550).  This feature is available in Postfix 2.1 and
	      later.

       reject_plaintext_session
	      Reject the request when the connection is not encrypted.	This  restriction  should
	      not  be  used  before  the client has had a chance to negotiate encryption with the
	      AUTH or STARTTLS commands.
	      The plaintext_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests (default:  450).  This feature is available in Postfix 2.3 and later.

       reject_unauth_pipelining
	      Reject  the  request  when the client sends SMTP commands ahead of time where it is
	      not allowed, or when the client sends SMTP commands ahead of time  without  knowing
	      that  Postfix actually supports ESMTP command pipelining. This stops mail from bulk
	      mail software that improperly uses ESMTP command pipelining in order  to	speed  up
	      deliveries.
	      With  Postfix  2.6  and  later, the SMTP server sets a per-session flag whenever it
	      detects  illegal	pipelining,  including	pipelined  EHLO  or  HELO  commands.  The
	      reject_unauth_pipelining feature simply tests whether the flag was set at any point
	      in time during the session.
	      With older Postfix versions, reject_unauth_pipelining checks the current status  of
	      the  input  read	queue,	and  its  usage is not recommended in contexts other than
	      smtpd_data_restrictions.

       reject Reject the request. This restriction is useful at the end of a restriction list, to
	      make  the  default policy explicit.  The reject_code configuration parameter speci-
	      fies the response code for rejected requests (default: 554).

       sleep seconds
	      Pause for the specified number of seconds and proceed with the next restriction  in
	      the list, if any. This may stop zombie mail when used as:
	      /etc/postfix/main.cf:
		  smtpd_client_restrictions =
		      sleep 1, reject_unauth_pipelining
		  smtpd_delay_reject = no
	      This feature is available in Postfix 2.3.

       warn_if_reject
	      Change  the  meaning  of the next restriction, so that it logs a warning instead of
	      rejecting a request (look for logfile records that contain "reject_warning").  This
	      is  useful  for  testing	new  restrictions in a "live" environment without risking
	      unnecessary loss of mail.

       Other restrictions that are valid in this context:

       o      SMTP command specific restrictions that are described under the smtpd_helo_restric-
	      tions,  smtpd_sender_restrictions  or smtpd_recipient_restrictions parameters. When
	      helo, sender or recipient restrictions are listed under  smtpd_client_restrictions,
	      they    have    effect	only   with   "smtpd_delay_reject   =	yes",	so   that
	      $smtpd_client_restrictions is evaluated at the time of the RCPT TO command.

       Example:

       smtpd_client_restrictions = permit_mynetworks, reject_unknown_client_hostname

smtpd_command_filter (default: empty)
       A mechanism to transform commands from remote SMTP clients.  This is a last-resort tool to
       work  around  client  commands  that break inter-operability with the Postfix SMTP server.
       Other uses involve fault injection to test Postfix's handling of invalid commands.

       Specify the name of a "type:table" lookup table. The search string is the SMTP command  as
       received  from  the  remote  SMTP  client, except that initial whitespace and the trailing
       <CR><LF> are removed.  The result value is executed by the Postfix SMTP server.

       There is no need to use smtpd_command_filter for the following cases:

       o      Use "resolve_numeric_domain = yes" to accept "user@ipaddress".

       o      Postfix already accepts the correct form "user@[ipaddress]". Use virtual_alias_maps
	      or canonical_maps to translate these into domain names if necessary.

       o      Use  "strict_rfc821_envelopes  =	no"  to  accept  "RCPT	TO:<User Name <user@exam-
	      ple.com>>". Postfix will ignore the "User Name" part and deliver to the <user@exam-
	      ple.com> address.

       Examples of problems that can be solved with the smtpd_command_filter feature:

       /etc/postfix/main.cf:
	   smtpd_command_filter = pcre:/etc/postfix/command_filter

       /etc/postfix/command_filter:
	   # Work around clients that send malformed HELO commands.
	   /^HELO\s*$/ HELO domain.invalid

	   # Work around clients that send empty lines.
	   /^\s*$/     NOOP

	   # Work around clients that send RCPT TO:<'user@domain'>.
	   # WARNING: do not lose the parameters that follow the address.
	   /^RCPT\s+TO:\s*<'([^[:space:]]+)'>(.*)/     RCPT TO:<$1>$2

	   # Bounce-never mail sink. Use notify_classes=bounce,resource,software
	   # to send bounced mail to the postmaster (with message body removed).
	   /^(RCPT\s+TO:.*?)\bNOTIFY=\S+\b(.*)/ $1 NOTIFY=NEVER $2
	   /^(RCPT\s+TO:.*)/			$1 NOTIFY=NEVER

       This feature is available in Postfix 2.7.

smtpd_data_restrictions (default: empty)
       Optional  access  restrictions  that the Postfix SMTP server applies in the context of the
       SMTP DATA command.  See SMTPD_ACCESS_README, section "Delayed evaluation  of  SMTP  access
       restriction lists" for a discussion of evaluation context and time.

       This feature is available in Postfix 2.0 and later.

       Specify	a  list  of  restrictions,  separated by commas and/or whitespace.  Continue long
       lines by starting the next line with whitespace.  Restrictions are applied in the order as
       specified; the first restriction that matches wins.

       The following restrictions are valid in this context:

       o      Generic  restrictions that can be used in any SMTP command context, described under
	      smtpd_client_restrictions.

       o      SMTP  command  specific  restrictions  described	under  smtpd_client_restrictions,
	      smtpd_helo_restrictions, smtpd_sender_restrictions or smtpd_recipient_restrictions.

       o      However, no recipient information is available in the case of multi-recipient mail.
	      Acting on only one recipient would be misleading, because any decision will  affect
	      all  recipients  equally.  Acting  on  all recipients would require a possibly very
	      large amount of memory, and would also be  misleading  for  the  reasons	mentioned
	      before.

       Examples:

       smtpd_data_restrictions = reject_unauth_pipelining
       smtpd_data_restrictions = reject_multi_recipient_bounce

smtpd_delay_open_until_valid_rcpt (default: yes)
       Postpone  the start of an SMTP mail transaction until a valid RCPT TO command is received.
       Specify "no" to create a mail transaction as soon as the SMTP server receives a valid MAIL
       FROM command.

       With  sites that reject lots of mail, the default setting reduces the use of disk, CPU and
       memory resources. The downside is that rejected recipients are logged with NOQUEUE instead
       of a mail transaction ID. This complicates the logfile analysis of multi-recipient mail.

       This feature is available in Postfix 2.3 and later.

smtpd_delay_reject (default: yes)
       Wait   until   the   RCPT   TO	command   before  evaluating  $smtpd_client_restrictions,
       $smtpd_helo_restrictions and $smtpd_sender_restrictions, or wait until  the  ETRN  command
       before evaluating $smtpd_client_restrictions and $smtpd_helo_restrictions.

       This  feature  is turned on by default because some clients apparently mis-behave when the
       Postfix SMTP server rejects commands before RCPT TO.

       The default setting has one major benefit: it allows  Postfix  to  log  recipient  address
       information when rejecting a client name/address or sender address, so that it is possible
       to find out whose mail is being rejected.

smtpd_discard_ehlo_keyword_address_maps (default: empty)
       Lookup tables, indexed by the remote SMTP client address, with case insensitive	lists  of
       EHLO keywords (pipelining, starttls, auth, etc.) that the SMTP server will not send in the
       EHLO response to a remote SMTP client. See smtpd_discard_ehlo_keywords for  details.   The
       table is not searched by hostname for robustness reasons.

       This feature is available in Postfix 2.2 and later.

smtpd_discard_ehlo_keywords (default: empty)
       A  case insensitive list of EHLO keywords (pipelining, starttls, auth, etc.) that the SMTP
       server will not send in the EHLO response to a remote SMTP client.

       This feature is available in Postfix 2.2 and later.

       Notes:

       o      Specify the silent-discard pseudo keyword to prevent this action from being logged.

       o      Use the smtpd_discard_ehlo_keyword_address_maps feature to  discard  EHLO  keywords
	      selectively.

smtpd_end_of_data_restrictions (default: empty)
       Optional  access  restrictions  that the Postfix SMTP server applies in the context of the
       SMTP END-OF-DATA command.  See SMTPD_ACCESS_README, section "Delayed  evaluation  of  SMTP
       access restriction lists" for a discussion of evaluation context and time.

       This feature is available in Postfix 2.2 and later.

       See smtpd_data_restrictions for details and limitations.

smtpd_enforce_tls (default: no)
       Mandatory TLS: announce STARTTLS support to SMTP clients, and require that clients use TLS
       encryption.  According to RFC 2487 this MUST NOT be applied in case of  a  publicly-refer-
       enced  SMTP  server.   This  option is off by default and should be used only on dedicated
       servers.

       Note 1: "smtpd_enforce_tls = yes" implies "smtpd_tls_auth_only = yes".

       Note 2: when invoked via "sendmail -bs", Postfix will never offer STARTTLS due to insuffi-
       cient privileges to access the server private key. This is intended behavior.

       This  feature  is  available  in  Postfix  2.2  and  later. With Postfix 2.3 and later use
       smtpd_tls_security_level instead.

smtpd_error_sleep_time (default: 1s)
       With Postfix version 2.1 and later: the SMTP server response delay after a client has made
       more  than  $smtpd_soft_error_limit errors, and fewer than $smtpd_hard_error_limit errors,
       without delivering mail.

       With Postfix version 2.0 and earlier: the SMTP server delay before sending a  reject  (4xx
       or 5xx) response, when the client has made fewer than $smtpd_soft_error_limit errors with-
       out delivering mail.

smtpd_etrn_restrictions (default: empty)
       Optional SMTP server access restrictions in the context of a  client  ETRN  request.   See
       SMTPD_ACCESS_README,  section  "Delayed evaluation of SMTP access restriction lists" for a
       discussion of evaluation context and time.

       The Postfix ETRN implementation accepts only destinations that are eligible for the  Post-
       fix "fast flush" service. See the ETRN_README file for details.

       Specify	a  list  of  restrictions,  separated by commas and/or whitespace.  Continue long
       lines by starting the next line with whitespace.  Restrictions are applied in the order as
       specified; the first restriction that matches wins.

       The  following  restrictions are specific to the domain name information received with the
       ETRN command.

       check_etrn_access type:table
	      Search the specified access database  for  the  ETRN  domain  name  or  its  parent
	      domains. See the access(5) manual page for details.

       Other restrictions that are valid in this context:

       o      Generic  restrictions that can be used in any SMTP command context, described under
	      smtpd_client_restrictions.

       o      SMTP command specific restrictions described  under  smtpd_client_restrictions  and
	      smtpd_helo_restrictions.

       Example:

       smtpd_etrn_restrictions = permit_mynetworks, reject

smtpd_expansion_filter (default: see postconf -d output)
       What  characters are allowed in $name expansions of RBL reply templates. Characters not in
       the allowed set are replaced by "_".  Use C like escapes  to  specify  special  characters
       such as whitespace.

       This parameter is not subjected to $parameter expansion.

       This feature is available in Postfix 2.0 and later.

smtpd_forbidden_commands (default: CONNECT, GET, POST)
       List  of  commands that cause the Postfix SMTP server to immediately terminate the session
       with a 221 code. This can be used to disconnect clients that obviously  attempt	to  abuse
       the system. In addition to the commands listed in this parameter, commands that follow the
       "Label:" format of message headers will also cause a disconnect.

       This feature is available in Postfix 2.2 and later.

smtpd_hard_error_limit (default: normal: 20, overload: 1)
       The maximal number of errors a remote SMTP client is allowed to	make  without  delivering
       mail. The Postfix SMTP server disconnects when the limit is exceeded. Normally the default
       limit is 20, but it changes under overload to just 1. With Postfix 2.5  and  earlier,  the
       SMTP server always allows up to 20 errors by default.

smtpd_helo_required (default: no)
       Require	that  a remote SMTP client introduces itself with the HELO or EHLO command before
       sending the MAIL command or other commands that require EHLO negotiation.

       Example:

       smtpd_helo_required = yes

smtpd_helo_restrictions (default: empty)
       Optional restrictions that the Postfix SMTP server applies in the context of the SMTP HELO
       command.   See SMTPD_ACCESS_README, section "Delayed evaluation of SMTP access restriction
       lists" for a discussion of evaluation context and time.

       The default is to permit everything.

       Note: specify "smtpd_helo_required = yes"  to  fully  enforce  this  restriction  (without
       "smtpd_helo_required = yes", a client can simply skip smtpd_helo_restrictions by not send-
       ing HELO or EHLO).

       Specify a list of restrictions, separated by  commas  and/or  whitespace.   Continue  long
       lines by starting the next line with whitespace.  Restrictions are applied in the order as
       specified; the first restriction that matches wins.

       The following restrictions are specific to the hostname information received with the HELO
       or EHLO command.

       check_helo_access type:table
	      Search  the  specified  access(5)  database for the HELO or EHLO hostname or parent
	      domains, and execute the corresponding action.  Note: specify  "smtpd_helo_required
	      =  yes"  to  fully enforce this restriction (without "smtpd_helo_required = yes", a
	      client can simply skip check_helo_access by not sending HELO or EHLO).

       check_helo_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the HELO or EHLO host-
	      name,  and  execute  the	corresponding  action.	 Note  1: a result of "OK" is not
	      allowed for safety reasons. Instead, use DUNNO in order to exclude  specific  hosts
	      from blacklists.	Note 2: specify "smtpd_helo_required = yes" to fully enforce this
	      restriction  (without  "smtpd_helo_required  =  yes",  a	client	can  simply  skip
	      check_helo_mx_access  by	not  sending HELO or EHLO).  This feature is available in
	      Postfix 2.1 and later.

       check_helo_ns_access type:table
	      Search the specified access(5) database for the DNS servers for the  HELO  or  EHLO
	      hostname,  and  execute  the corresponding action.  Note 1: a result of "OK" is not
	      allowed for safety reasons. Instead, use DUNNO in order to exclude  specific  hosts
	      from blacklists.	Note 2: specify "smtpd_helo_required = yes" to fully enforce this
	      restriction  (without  "smtpd_helo_required  =  yes",  a	client	can  simply  skip
	      check_helo_ns_access  by	not  sending  HELO or EHLO). This feature is available in
	      Postfix 2.1 and later.

       reject_invalid_helo_hostname (with Postfix < 2.3: reject_invalid_hostname)
	      Reject the request when the HELO or EHLO hostname syntax is invalid. Note:  specify
	      "smtpd_helo_required   =	 yes"	to   fully   enforce  this  restriction  (without
	      "smtpd_helo_required = yes", a client can simply skip  reject_invalid_helo_hostname
	      by not sending HELO or EHLO).
	      The  invalid_hostname_reject_code specifies the response code for rejected requests
	      (default: 501).

       reject_non_fqdn_helo_hostname (with Postfix < 2.3: reject_non_fqdn_hostname)
	      Reject the request when the HELO or EHLO hostname is not in fully-qualified  domain
	      form,  as  required  by the RFC. Note: specify "smtpd_helo_required = yes" to fully
	      enforce this restriction (without "smtpd_helo_required = yes", a client can  simply
	      skip reject_non_fqdn_helo_hostname by not sending HELO or EHLO).
	      The  non_fqdn_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests (default: 504).

       reject_rhsbl_helo rbl_domain=d.d.d.d
	      Reject the request when the HELO or EHLO hostname hostname is  listed  with  the	A
	      record  "d.d.d.d"  under rbl_domain (Postfix version 2.1 and later only).  Each "d"
	      is a number, or a pattern inside "[]" that contains one or more ";"-separated  num-
	      bers or number..number ranges (Postfix version 2.8 and later).  If no "=d.d.d.d" is
	      specified, reject the request when the HELO or EHLO hostname is listed with  any	A
	      record  under  rbl_domain. See the reject_rbl_client description for additional RBL
	      related configuration parameters.  Note: specify	"smtpd_helo_required  =  yes"  to
	      fully  enforce  this restriction (without "smtpd_helo_required = yes", a client can
	      simply skip reject_rhsbl_helo by not sending HELO or EHLO). This feature is  avail-
	      able in Postfix 2.0 and later.

       reject_unknown_helo_hostname (with Postfix < 2.3: reject_unknown_hostname)
	      Reject the request when the HELO or EHLO hostname has no DNS A or MX record.
	      The  unknown_hostname_reject_code  parameter  specifies the numerical response code
	      for rejected requests (default: 450).
	      The unknown_helo_hostname_tempfail_action parameter specifies the  action  after	a
	      temporary  DNS error (default: defer_if_permit). Note: specify "smtpd_helo_required
	      = yes" to fully enforce this restriction (without "smtpd_helo_required  =  yes",	a
	      client can simply skip reject_unknown_helo_hostname by not sending HELO or EHLO).

       Other restrictions that are valid in this context:

       o      Generic  restrictions that can be used in any SMTP command context, described under
	      smtpd_client_restrictions.

       o      Client  hostname	or  network  address  specific	 restrictions	described   under
	      smtpd_client_restrictions.

       o      SMTP  command  specific  restrictions  described under smtpd_sender_restrictions or
	      smtpd_recipient_restrictions.  When sender or  recipient	restrictions  are  listed
	      under  smtpd_helo_restrictions,  they  have  effect only with "smtpd_delay_reject =
	      yes", so that $smtpd_helo_restrictions is evaluated at the time of the RCPT TO com-
	      mand.

       Examples:

       smtpd_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname
       smtpd_helo_restrictions = permit_mynetworks, reject_unknown_helo_hostname

smtpd_history_flush_threshold (default: 100)
       The  maximal  number  of  lines	in  the  Postfix SMTP server command history before it is
       flushed upon receipt of EHLO, RSET, or end of DATA.

smtpd_junk_command_limit (default: normal: 100, overload: 1)
       The number of junk commands (NOOP, VRFY, ETRN or RSET) that a remote SMTP client can  send
       before  the  Postfix SMTP server starts to increment the error counter with each junk com-
       mand.   The  junk  command  count  is  reset  after  mail  is  delivered.   See	also  the
       smtpd_error_sleep_time  and smtpd_soft_error_limit configuration parameters.  Normally the
       default limit is 100, but it changes under overload to just 1. With Postfix 2.5	and  ear-
       lier, the SMTP server always allows up to 100 junk commands by default.

smtpd_milters (default: empty)
       A  list	of  Milter  (mail  filter) applications for new mail that arrives via the Postfix
       smtpd(8) server.  See the MILTER_README document for details.

       This feature is available in Postfix 2.3 and later.

smtpd_noop_commands (default: empty)
       List of commands that the Postfix SMTP server replies to with "250 Ok", without doing  any
       syntax checks and without changing state.  This list overrides any commands built into the
       Postfix SMTP server.

smtpd_null_access_lookup_key (default: <>)
       The lookup key to be used in SMTP access(5) tables instead of the null sender address.

smtpd_peername_lookup (default: yes)
       Attempt to look up the remote SMTP client hostname, and verify that the name  matches  the
       client  IP address. A client name is set to "unknown" when it cannot be looked up or veri-
       fied, or when name lookup is disabled.  Turning off name lookup reduces delays due to  DNS
       lookup and increases the maximal inbound delivery rate.

       This feature is available in Postfix 2.3 and later.

smtpd_policy_service_max_idle (default: 300s)
       The time after which an idle SMTPD policy service connection is closed.

       This feature is available in Postfix 2.1 and later.

smtpd_policy_service_max_ttl (default: 1000s)
       The time after which an active SMTPD policy service connection is closed.

       This feature is available in Postfix 2.1 and later.

smtpd_policy_service_timeout (default: 100s)
       The  time  limit  for connecting to, writing to or receiving from a delegated SMTPD policy
       server.

       This feature is available in Postfix 2.1 and later.

smtpd_proxy_ehlo (default: $myhostname)
       How the Postfix SMTP server announces itself to the proxy filter.  By default, the Postfix
       hostname is used.

       This feature is available in Postfix 2.1 and later.

smtpd_proxy_filter (default: empty)
       The hostname and TCP port of the mail filtering proxy server.  The proxy receives all mail
       from the Postfix SMTP server, and is supposed to give the result to another  Postfix  SMTP
       server process.

       Specify "host:port" or "inet:host:port" for a TCP endpoint, or "unix:pathname" for a UNIX-
       domain endpoint. The host can be specified as an IP address or as a symbolic name;  no  MX
       lookups are done.  When no "host" or "host:"  are specified, the local machine is assumed.
       Pathname interpretation is relative to the Postfix queue directory.

       This feature is available in Postfix 2.1 and later.

       The "inet:" and "unix:" prefixes are available in Postfix 2.3 and later.

smtpd_proxy_options (default: empty)
       List of options that control how the Postfix SMTP server communicates with a  before-queue
       content filter. Specify zero or more of the following, separated by comma or whitespace.

       speed_adjust
	      Do  not  connect	to a before-queue content filter until an entire message has been
	      received. This reduces the number of simultaneous before-queue content filter  pro-
	      cesses.

       NOTE  1:  A  filter  must  not selectively reject recipients of a multi-recipient message.
       Rejecting all recipients is OK, as is accepting all recipients.

       NOTE 2:	This  feature  increases  the  minimum	amount	of  free  queue  space	by  $mes-
       sage_size_limit. The extra space is needed to save the message to a temporary file.

       This feature is available in Postfix 2.7 and later.

smtpd_proxy_timeout (default: 100s)
       The  time limit for connecting to a proxy filter and for sending or receiving information.
       When a connection fails the client gets a generic error message while more detailed infor-
       mation is logged to the maillog file.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1 and later.

smtpd_recipient_limit (default: 1000)
       The maximal number of recipients that the Postfix SMTP server accepts per message delivery
       request.

smtpd_recipient_overshoot_limit (default: 1000)
       The  number of recipients that a remote SMTP client can send in excess of the limit speci-
       fied with $smtpd_recipient_limit, before the Postfix SMTP server increments  the  per-ses-
       sion error count for each excess recipient.

smtpd_recipient_restrictions (default: permit_mynetworks, reject_unauth_destination)
       The access restrictions that the Postfix SMTP server applies in the context of the RCPT TO
       command.  See SMTPD_ACCESS_README, section "Delayed evaluation of SMTP access  restriction
       lists" for a discussion of evaluation context and time.

       By default, the Postfix SMTP server accepts:

       o      Mail from clients whose IP address matches $mynetworks, or:

       o      Mail  to	remote	destinations that match $relay_domains, except for addresses that
	      contain sender-specified routing (user@elsewhere@domain), or:

       o      Mail to  local  destinations  that  match  $inet_interfaces  or  $proxy_interfaces,
	      $mydestination, $virtual_alias_domains, or $virtual_mailbox_domains.

       IMPORTANT: If you change this parameter setting, you must specify at least one of the fol-
       lowing restrictions. Otherwise Postfix will refuse to receive mail:

	   reject, defer, defer_if_permit, reject_unauth_destination

       Specify a list of restrictions, separated by  commas  and/or  whitespace.   Continue  long
       lines by starting the next line with whitespace.  Restrictions are applied in the order as
       specified; the first restriction that matches wins.

       The following restrictions are specific to the recipient address that is received with the
       RCPT TO command.

       check_recipient_access type:table
	      Search  the  specified access(5) database for the resolved RCPT TO address, domain,
	      parent domains, or localpart@, and execute the corresponding action.

       check_recipient_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the	RCPT  TO  domain,
	      and  execute  the  corresponding action.	Note: a result of "OK" is not allowed for
	      safety reasons. Instead, use DUNNO in order to exclude specific hosts  from  black-
	      lists.  This feature is available in Postfix 2.1 and later.

       check_recipient_ns_access type:table
	      Search the specified access(5) database for the DNS servers for the RCPT TO domain,
	      and execute the corresponding action.  Note: a result of "OK" is	not  allowed  for
	      safety  reasons.	Instead, use DUNNO in order to exclude specific hosts from black-
	      lists.  This feature is available in Postfix 2.1 and later.

       permit_auth_destination
	      Permit the request when one of the following is true:

       o      Postfix is mail forwarder: the resolved RCPT TO domain matches $relay_domains or	a
	      subdomain thereof, and the address contains no sender-specified routing (user@else-
	      where@domain),

       o      Postfix is the final destination: the resolved RCPT TO domain  matches  $mydestina-
	      tion,   $inet_interfaces,   $proxy_interfaces,   $virtual_alias_domains,	or  $vir-
	      tual_mailbox_domains,  and  the  address	contains  no   sender-specified   routing
	      (user@elsewhere@domain).

       permit_mx_backup
	      Permit  the request when the local mail system is backup MX for the RCPT TO domain,
	      or when the domain is an authorized destination  (see  permit_auth_destination  for
	      definition).

       o      Safety: permit_mx_backup does not accept addresses that have sender-specified rout-
	      ing information (example: user@elsewhere@domain).

       o      Safety: permit_mx_backup can be vulnerable to mis-use when access is not restricted
	      with permit_mx_backup_networks.

       o      Safety:  as  of Postfix version 2.3, permit_mx_backup no longer accepts the address
	      when the local mail system is primary MX for the recipient domain.  Exception: per-
	      mit_mx_backup  accepts the address when it specifies an authorized destination (see
	      permit_auth_destination for definition).

       o      Limitation: mail may be rejected in case of a temporary  DNS  lookup  problem  with
	      Postfix prior to version 2.0.

       reject_non_fqdn_recipient
	      Reject  the request when the RCPT TO address is not in fully-qualified domain form,
	      as required by the RFC.
	      The  non_fqdn_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests (default: 504).

       reject_rhsbl_recipient rbl_domain=d.d.d.d
	      Reject  the  request  when the RCPT TO domain is listed with the A record "d.d.d.d"
	      under rbl_domain (Postfix version 2.1 and later only).  Each "d" is a number, or	a
	      pattern inside "[]" that contains one or more ";"-separated numbers or number..num-
	      ber ranges (Postfix version 2.8 and later). If no "=d.d.d.d" is  specified,  reject
	      the request when the RCPT TO domain is listed with any A record under rbl_domain.
	      The  maps_rbl_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests (default: 554); the  default_rbl_reply  parameter  specifies  the  default
	      server reply; and the rbl_reply_maps parameter specifies tables with server replies
	      indexed by rbl_domain.  This feature is available in Postfix version 2.0 and later.

       reject_unauth_destination
	      Reject the request unless one of the following is true:

       o      Postfix is mail forwarder: the resolved RCPT TO domain matches $relay_domains or	a
	      subdomain   thereof,   and   contains   no   sender-specified  routing  (user@else-
	      where@domain),

       o      Postfix is the final destination: the resolved RCPT TO domain  matches  $mydestina-
	      tion,   $inet_interfaces,   $proxy_interfaces,   $virtual_alias_domains,	or  $vir-
	      tual_mailbox_domains,  and  contains  no	 sender-specified   routing   (user@else-
	      where@domain).
	       The  relay_domains_reject_code  parameter specifies the response code for rejected
	      requests (default: 554).

       reject_unknown_recipient_domain
	      Reject the request when Postfix is not final destination for the recipient  domain,
	      and  the	RCPT  TO  domain has no DNS A or MX record, or when it has a malformed MX
	      record such as a record with a zero-length MX hostname  (Postfix	version  2.3  and
	      later).
	      The unknown_address_reject_code parameter specifies the numerical response code for
	      rejected requests (default: 450).  The response is always 450 in case of	a  tempo-
	      rary DNS error.
	      The  unknown_address_tempfail_action  parameter specifies the action after a tempo-
	      rary DNS error (default: defer_if_permit).

       reject_unlisted_recipient (with Postfix version 2.0: check_recipient_maps)
	      Reject the request when the RCPT TO address is not listed  in  the  list	of  valid
	      recipients  for its domain class. See the smtpd_reject_unlisted_recipient parameter
	      description for details.	This feature is available in Postfix 2.1 and later.

       reject_unverified_recipient
	      Reject the request when mail to the RCPT TO address is known to bounce, or when the
	      recipient  address  destination is not reachable.  Address verification information
	      is managed by the verify(8) server; see the  ADDRESS_VERIFICATION_README	file  for
	      details.
	      The  unverified_recipient_reject_code  parameter	specifies  the numerical response
	      code when an address is known to bounce (default: 450, change into 550 when you are
	      confident that it is safe to do so).
	      The unverified_recipient_defer_code parameter specifies the numerical response code
	      when an address probe failed due to a temporary problem (default: 450).
	      The  unverified_recipient_tempfail_action  parameter  specifies  the  action  after
	      addres probe failure due to a temporary problem (default: defer_if_permit).
	      This feature is available in Postfix 2.1 and later.

       Other restrictions that are valid in this context:

       o      Generic  restrictions that can be used in any SMTP command context, described under
	      smtpd_client_restrictions.

       o      SMTP  command  specific  restrictions  described	under  smtpd_client_restrictions,
	      smtpd_helo_restrictions and smtpd_sender_restrictions.

       Example:

       smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination

smtpd_reject_footer (default: empty)
       Optional information that is appended after each SMTP server 4XX or 5XX response.

       Example:

       /etc/postfix/main.cf:
	   smtpd_reject_footer = For assistance, call 800-555-0101.
	    Please provide the following information in your problem report:
	    time ($localtime), client ($client_address) and server
	    ($server_name).

       Server response:

	   550-5.5.1 <user@example> Recipient address rejected: User unknown
	   550 5.5.1 For assistance, call 800-555-0101. Please provide the
	   following information in your problem report: time (Jan 4 15:42:00),
	   client (192.168.1.248) and server (mail1.example.com).

       Note:  the above text is meant to make it easier to find the Postfix logfile records for a
       failed SMTP session. The text itself is not logged to the Postfix  SMTP	server's  maillog
       file.

       Be  sure  to  keep  the text as short as possible. Long text may be truncated before it is
       logged to the remote SMTP client's maillog file, or before it is returned to the sender in
       a delivery status notification.

       This  feature  supports a limited number of $name attributes in the footer text. These are
       replaced by their current value for the SMTP session:

       client_address
	      The Client IP address that is logged in the maillog file.

       client_port
	      The client TCP port that is logged in the maillog file.

       localtime
	      The server local time (Mmm dd hh:mm:ss) that is logged in the maillog file.

       server_name
	      The server's myhostname value.  This attribute is made  available  for  sites  with
	      multiple	MTAs (perhaps behind a load-balancer), where the server name can help the
	      server support team to quickly find the right log files.

       Notes:

       o      NOT SUPPORTED are other attributes such as sender, recipient,  or  main.cf  parame-
	      ters.

       o      For safety reasons, text that does not match $smtpd_expansion_filter is censored.

       This  feature  supports the two-character sequence \n as a request for a line break in the
       footer text. Postfix automatically inserts after each  line  break  the	three-digit  SMTP
       reply code (and optional enhanced status code) from the original Postfix reject message.

       This feature is available in Postfix 2.8 and later.

smtpd_reject_unlisted_recipient (default: yes)
       Request	that  the  Postfix SMTP server rejects mail for unknown recipient addresses, even
       when no explicit reject_unlisted_recipient access restriction is specified. This  prevents
       the Postfix queue from filling up with undeliverable MAILER-DAEMON messages.

       An  address  is	always considered "known" when it matches a virtual(5) alias or a canoni-
       cal(5) mapping.

       o      The recipient domain matches $mydestination, $inet_interfaces or $proxy_interfaces,
	      but the recipient is not listed in $local_recipient_maps, and $local_recipient_maps
	      is not null.

       o      The recipient domain matches $virtual_alias_domains but the recipient is not listed
	      in $virtual_alias_maps.

       o      The  recipient  domain  matches  $virtual_mailbox_domains  but the recipient is not
	      listed in $virtual_mailbox_maps, and $virtual_mailbox_maps is not null.

       o      The recipient domain matches $relay_domains but the  recipient  is  not  listed  in
	      $relay_recipient_maps, and $relay_recipient_maps is not null.

       This feature is available in Postfix 2.1 and later.

smtpd_reject_unlisted_sender (default: no)
       Request that the Postfix SMTP server rejects mail from unknown sender addresses, even when
       no explicit reject_unlisted_sender access restriction is specified. This can slow down  an
       explosion of forged mail from worms or viruses.

       An  address  is	always considered "known" when it matches a virtual(5) alias or a canoni-
       cal(5) mapping.

       o      The sender domain matches $mydestination,  $inet_interfaces  or  $proxy_interfaces,
	      but the sender is not listed in $local_recipient_maps, and $local_recipient_maps is
	      not null.

       o      The sender domain matches $virtual_alias_domains but the sender is  not  listed  in
	      $virtual_alias_maps.

       o      The  sender domain matches $virtual_mailbox_domains but the sender is not listed in
	      $virtual_mailbox_maps, and $virtual_mailbox_maps is not null.

       o      The  sender  domain  matches  $relay_domains  but  the  sender  is  not  listed  in
	      $relay_recipient_maps, and $relay_recipient_maps is not null.

       This feature is available in Postfix 2.1 and later.

smtpd_restriction_classes (default: empty)
       User-defined  aliases  for  groups of access restrictions. The aliases can be specified in
       smtpd_recipient_restrictions etc., and on the right-hand side of a Postfix  access(5)  ta-
       ble.

       One  major  application	is  for implementing per-recipient UCE control.  See the RESTRIC-
       TION_CLASS_README document for other examples.

smtpd_sasl_application_name (default: smtpd)
       The application name that the Postfix SMTP server uses  for  SASL  server  initialization.
       This  controls the name of the SASL configuration file. The default value is smtpd, corre-
       sponding to a SASL configuration file named smtpd.conf.

       This feature is available in Postfix 2.1 and 2.2. With  Postfix	2.3  it  was  renamed  to
       smtpd_sasl_path.

smtpd_sasl_auth_enable (default: no)
       Enable SASL authentication in the Postfix SMTP server. By default, the Postfix SMTP server
       does not use authentication.

       If a remote SMTP client is authenticated, the permit_sasl_authenticated access restriction
       can be used to permit relay access, like this:

	   smtpd_recipient_restrictions =
	       permit_mynetworks, permit_sasl_authenticated, ...

       To reject all SMTP connections from unauthenticated clients, specify "smtpd_delay_reject =
       yes" (which is the default) and use:

	   smtpd_client_restrictions = permit_sasl_authenticated, reject

       See the SASL_README file for SASL configuration and operation details.

smtpd_sasl_authenticated_header (default: no)
       Report the SASL authenticated user name in the smtpd(8) Received message header.

       This feature is available in Postfix 2.3 and later.

smtpd_sasl_exceptions_networks (default: empty)
       What remote SMTP clients the Postfix SMTP server will not offer AUTH support to.

       Some clients (Netscape 4 at least) have a bug that causes them  to  require  a  login  and
       password  whenever  AUTH  is  offered, whether it's necessary or not. To work around this,
       specify, for example, $mynetworks to prevent Postfix from offering AUTH to local clients.

       Specify a list of network/netmask patterns, separated by  commas  and/or  whitespace.  The
       mask  specifies	the  number  of  bits in the network part of a host address. You can also
       "/file/name" or "type:table" patterns.  A "/file/name" pattern is  replaced  by	its  con-
       tents;  a  "type:table" lookup table is matched when a table entry matches a lookup string
       (the lookup result is ignored).	Continue long lines by starting the next line with white-
       space.  Specify "!pattern" to exclude an address or network block from the list.  The form
       "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version  6  address  information  must  be   specified   inside   []	 in   the
       smtpd_sasl_exceptions_networks  value,  and in files specified with "/file/name".  IP ver-
       sion 6 addresses contain the ":"  character,  and  would  otherwise  be	confused  with	a
       "type:table" pattern.

       Example:

       smtpd_sasl_exceptions_networks = $mynetworks

       This feature is available in Postfix 2.1 and later.

smtpd_sasl_local_domain (default: empty)
       The name of the Postfix SMTP server's local SASL authentication realm.

       By default, the local authentication realm name is the null string.

       Examples:

       smtpd_sasl_local_domain = $mydomain
       smtpd_sasl_local_domain = $myhostname

smtpd_sasl_path (default: smtpd)
       Implementation-specific	information  that  the	Postfix SMTP server passes through to the
       SASL plug-in implementation that is selected with smtpd_sasl_type.  Typically this  speci-
       fies the name of a configuration file or rendezvous point.

       This  feature  is  available  in  Postfix 2.3 and later. In earlier releases it was called
       smtpd_sasl_application_name.

smtpd_sasl_security_options (default: noanonymous)
       Postfix SMTP server SASL security options; as of Postfix 2.3 the list  of  available  fea-
       tures depends on the SASL server implementation that is selected with smtpd_sasl_type.

       The following security features are defined for the cyrus server SASL implementation:

       Restrict  what authentication mechanisms the Postfix SMTP server will offer to the client.
       The list of available authentication mechanisms is system dependent.

       Specify zero or more of the following:

       noplaintext
	      Disallow methods that use plaintext passwords.

       noactive
	      Disallow methods subject to active (non-dictionary) attack.

       nodictionary
	      Disallow methods subject to passive (dictionary) attack.

       noanonymous
	      Disallow methods that allow anonymous authentication.

       forward_secrecy
	      Only allow methods that support forward secrecy (Dovecot only).

       mutual_auth
	      Only allow methods that provide mutual authentication  (not  available  with  Cyrus
	      SASL version 1).

       By default, the Postfix SMTP server accepts plaintext passwords but not anonymous logins.

       Warning:  it appears that clients try authentication methods in the order as advertised by
       the server (e.g., PLAIN ANONYMOUS CRAM-MD5) which means	that  if  you  disable	plaintext
       passwords, clients will log in anonymously, even when they should be able to use CRAM-MD5.
       So, if you disable plaintext logins, disable anonymous logins too.  Postfix treats  anony-
       mous login as no authentication.

       Example:

       smtpd_sasl_security_options = noanonymous, noplaintext

smtpd_sasl_tls_security_options (default: $smtpd_sasl_security_options)
       The  SASL  authentication  security  options  that  the	Postfix  SMTP server uses for TLS
       encrypted SMTP sessions.

       This feature is available in Postfix 2.2 and later.

smtpd_sasl_type (default: cyrus)
       The SASL plug-in type that the Postfix SMTP server  should  use	for  authentication.  The
       available types are listed with the "postconf -a" command.

       This feature is available in Postfix 2.3 and later.

smtpd_sender_login_maps (default: empty)
       Optional lookup table with the SASL login names that own sender (MAIL FROM) addresses.

       Specify	zero  or more "type:table" lookup tables. With lookups from indexed files such as
       DB or DBM, or from networked tables such as NIS, LDAP or SQL, the following search  opera-
       tions are done with a sender address of user@domain:

       1) user@domain
	      This table lookup is always done and has the highest precedence.

       2) user
	      This  table  lookup is done only when the domain part of the sender address matches
	      $myorigin, $mydestination, $inet_interfaces or $proxy_interfaces.

       3) @domain
	      This table lookup is done last and has the lowest precedence.

       In all cases the result of table lookup must be either "not found" or a list of SASL login
       names separated by comma and/or whitespace.

smtpd_sender_restrictions (default: empty)
       Optional restrictions that the Postfix SMTP server applies in the context of the MAIL FROM
       command.  See SMTPD_ACCESS_README, section "Delayed evaluation of SMTP access  restriction
       lists" for a discussion of evaluation context and time.

       The default is to permit everything.

       Specify	a  list  of  restrictions,  separated by commas and/or whitespace.  Continue long
       lines by starting the next line with whitespace.  Restrictions are applied in the order as
       specified; the first restriction that matches wins.

       The  following restrictions are specific to the sender address received with the MAIL FROM
       command.

       check_sender_access type:table
	      Search the specified access(5) database for the MAIL FROM address,  domain,  parent
	      domains, or localpart@, and execute the corresponding action.

       check_sender_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the MAIL FROM address,
	      and execute the corresponding action.  Note: a result of "OK" is	not  allowed  for
	      safety  reasons.	Instead, use DUNNO in order to exclude specific hosts from black-
	      lists.  This feature is available in Postfix 2.1 and later.

       check_sender_ns_access type:table
	      Search the specified access(5) database for the  DNS  servers  for  the  MAIL  FROM
	      address,	and  execute  the  corresponding  action.   Note: a result of "OK" is not
	      allowed for safety reasons. Instead, use DUNNO in order to exclude  specific  hosts
	      from blacklists.	This feature is available in Postfix 2.1 and later.

       reject_authenticated_sender_login_mismatch
	      Enforces	the  reject_sender_login_mismatch  restriction	for authenticated clients
	      only. This feature is available in Postfix version 2.1 and later.

       reject_non_fqdn_sender
	      Reject the request when the MAIL FROM address  is  not  in  fully-qualified  domain
	      form, as required by the RFC.
	      The  non_fqdn_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests (default: 504).

       reject_rhsbl_sender rbl_domain=d.d.d.d
	      Reject the request when the MAIL FROM domain is listed with the A record	"d.d.d.d"
	      under  rbl_domain (Postfix version 2.1 and later only).  Each "d" is a number, or a
	      pattern inside "[]" that contains one or more ";"-separated numbers or number..num-
	      ber  ranges  (Postfix version 2.8 and later). If no "=d.d.d.d" is specified, reject
	      the request when the MAIL FROM domain is listed with any A record under rbl_domain.
	      The  maps_rbl_reject_code  parameter  specifies  the  response  code  for  rejected
	      requests	(default:   554);  the	default_rbl_reply parameter specifies the default
	      server reply; and the rbl_reply_maps parameter specifies tables with server replies
	      indexed by rbl_domain.  This feature is available in Postfix 2.0 and later.

       reject_sender_login_mismatch
	      Reject  the  request  when $smtpd_sender_login_maps specifies an owner for the MAIL
	      FROM address, but the client is not (SASL) logged in  as	that  MAIL  FROM  address
	      owner;  or  when	the client is (SASL) logged in, but the client login name doesn't
	      own the MAIL FROM address according to $smtpd_sender_login_maps.

       reject_unauthenticated_sender_login_mismatch
	      Enforces the reject_sender_login_mismatch restriction for  unauthenticated  clients
	      only. This feature is available in Postfix version 2.1 and later.

       reject_unknown_sender_domain
	      Reject  the  request  when Postfix is not final destination for the sender address,
	      and the MAIL FROM address has no DNS A or MX record, or when it has a malformed  MX
	      record  such  as	a  record with a zero-length MX hostname (Postfix version 2.3 and
	      later).
	      The unknown_address_reject_code parameter specifies the numerical response code for
	      rejected	requests  (default: 450).  The response is always 450 in case of a tempo-
	      rary DNS error.
	      The unknown_address_tempfail_action parameter specifies the action after	a  tempo-
	      rary DNS error (default: defer_if_permit).

       reject_unlisted_sender
	      Reject  the  request  when the MAIL FROM address is not listed in the list of valid
	      recipients for its domain class.	See  the  smtpd_reject_unlisted_sender	parameter
	      description for details.	This feature is available in Postfix 2.1 and later.

       reject_unverified_sender
	      Reject  the  request when mail to the MAIL FROM address is known to bounce, or when
	      the sender address destination is not reachable.	Address verification  information
	      is  managed  by  the verify(8) server; see the ADDRESS_VERIFICATION_README file for
	      details.
	      The unverified_sender_reject_code parameter specifies the numerical  response  code
	      when an address is known to bounce (default: 450, change into 550 when you are con-
	      fident that it is safe to do so).
	      The unverified_sender_defer_code specifies the  numerical  response  code  when  an
	      address address probe failed due to a temporary problem (default: 450).
	      The  unverified_sender_tempfail_action parameter specifies the action after address
	      probe failure due to a temporary problem (default: defer_if_permit).
	      This feature is available in Postfix 2.1 and later.

       Other restrictions that are valid in this context:

       o      Generic restrictions that can be used in any SMTP command context, described  under
	      smtpd_client_restrictions.

       o      SMTP  command  specific  restrictions described under smtpd_client_restrictions and
	      smtpd_helo_restrictions.

       o      SMTP command specific restrictions  described  under  smtpd_recipient_restrictions.
	      When  recipient  restrictions are listed under smtpd_sender_restrictions, they have
	      effect only with "smtpd_delay_reject = yes", so that $smtpd_sender_restrictions  is
	      evaluated at the time of the RCPT TO command.

       Examples:

       smtpd_sender_restrictions = reject_unknown_sender_domain
       smtpd_sender_restrictions = reject_unknown_sender_domain,
	   check_sender_access hash:/etc/postfix/access

smtpd_service_name (default: smtpd)
       The  internal service that postscreen(8) forwards allowed connections to. In a future ver-
       sion there may be different classes of SMTP service.

       This feature is available in Postfix 2.8.

smtpd_soft_error_limit (default: 10)
       The number of errors a remote SMTP client is  allowed  to  make	without  delivering  mail
       before the Postfix SMTP server slows down all its responses.

       o      With Postfix version 2.1 and later, the Postfix SMTP server delays all responses by
	      $smtpd_error_sleep_time seconds.

       o      With Postfix versions 2.0 and earlier, the Postfix SMTP server delays all responses
	      by (number of errors) seconds.

smtpd_starttls_timeout (default: see postconf -d output)
       The  time  limit  for Postfix SMTP server write and read operations during TLS startup and
       shutdown handshake procedures. The current default value is stress-dependent. Before Post-
       fix version 2.8, it was fixed at 300s.

       This feature is available in Postfix 2.2 and later.

smtpd_timeout (default: normal: 300s, overload: 10s)
       The  time limit for sending a Postfix SMTP server response and for receiving a remote SMTP
       client request. Normally the default limit is 300s, but it changes under overload to  just
       10s.  With  Postfix  2.5  and earlier, the SMTP server always uses a time limit of 300s by
       default.

       Note: if you set SMTP time limits to very large values you may have to update  the  global
       ipc_timeout parameter.

       Time  units:  s	(seconds), m (minutes), h (hours), d (days), w (weeks).  The default time
       unit is s (seconds).

smtpd_tls_CAfile (default: empty)
       A file containing (PEM format) CA certificates of root CAs trusted to sign  either  remote
       SMTP  client  certificates  or intermediate CA certificates.  These are loaded into memory
       before the smtpd(8) server enters the chroot jail. If  the  number  of  trusted	roots  is
       large, consider using smtpd_tls_CApath instead, but note that the latter directory must be
       present in the chroot jail if the smtpd(8) server is chrooted. This file may also be  used
       to  augment the server certificate trust chain, but it is best to include all the required
       certificates directly in the server certificate file.

       Specify "tls_append_default_CA = no" to prevent Postfix from appending the system-supplied
       default CAs and trusting third-party certificates.

       By   default  (see  smtpd_tls_ask_ccert),  client  certificates	are  not  requested,  and
       smtpd_tls_CAfile should remain empty. If you do make use of client certificates, the  dis-
       tinguished  names (DNs) of the certificate authorities listed in smtpd_tls_CAfile are sent
       to the remote SMTP client in the client certificate request message.  MUAs  with  multiple
       client  certificates  may  use the list of preferred certificate authorities to select the
       correct client certificate.  You may want to put your "preferred" CA or CAs in this  file,
       and install other trusted CAs in $smtpd_tls_CApath.

       Example:

       smtpd_tls_CAfile = /etc/postfix/CAcert.pem

       This feature is available in Postfix 2.2 and later.

smtpd_tls_CApath (default: empty)
       A  directory  containing  (PEM  format) CA certificates of root CAs trusted to sign either
       remote SMTP client certificates or intermediate CA certificates. Do not forget  to  create
       the  necessary  "hash"  links  with,  for  example, "$OPENSSL_HOME/bin/c_rehash /etc/post-
       fix/certs". To use smtpd_tls_CApath in chroot mode, this directory (or  a  copy)  must  be
       inside the chroot jail.

       Specify "tls_append_default_CA = no" to prevent Postfix from appending the system-supplied
       default CAs and trusting third-party certificates.

       By  default  (see  smtpd_tls_ask_ccert),  client  certificates  are  not  requested,   and
       smtpd_tls_CApath  should remain empty. In contrast to smtpd_tls_CAfile, DNs of certificate
       authorities installed in $smtpd_tls_CApath are not  included  in  the  client  certificate
       request message. MUAs with multiple client certificates may use the list of preferred cer-
       tificate authorities to select the correct client certificate.  You may want to	put  your
       "preferred"  CA	or  CAs  in  $smtpd_tls_CAfile,  and install the remaining trusted CAs in
       $smtpd_tls_CApath.

       Example:

       smtpd_tls_CApath = /etc/postfix/certs

       This feature is available in Postfix 2.2 and later.

smtpd_tls_always_issue_session_ids (default: yes)
       Force the Postfix SMTP server to issue a TLS session id, even when TLS session caching  is
       turned  off  (smtpd_tls_session_cache_database is empty). This behavior is compatible with
       Postfix < 2.3.

       With Postfix 2.3 and later the Postfix SMTP server can disable session id generation  when
       TLS  session  caching  is turned off. This keeps clients from caching sessions that almost
       certainly cannot be re-used.

       By default, the Postfix SMTP server always generates TLS session ids. This works around	a
       known defect in mail client applications such as MS Outlook, and may also prevent interop-
       erability issues with other MTAs.

       Example:

       smtpd_tls_always_issue_session_ids = no

       This feature is available in Postfix 2.3 and later.

smtpd_tls_ask_ccert (default: no)
       Ask a remote SMTP client for a client certificate. This information is needed for certifi-
       cate based mail relaying with, for example, the permit_tls_clientcerts feature.

       Some clients such as Netscape will either complain if no certificate is available (for the
       list of CAs in $smtpd_tls_CAfile) or will offer multiple  client  certificates  to  choose
       from. This may be annoying, so this option is "off" by default.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_auth_only (default: no)
       When TLS encryption is optional in the Postfix SMTP server, do not announce or accept SASL
       authentication over unencrypted connections.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_ccert_verifydepth (default: 9)
       The verification depth for remote SMTP client certificates. A depth of 1 is sufficient  if
       the issuing CA is listed in a local CA file.

       The  default  verification depth is 9 (the OpenSSL default) for compatibility with earlier
       Postfix behavior. Prior to Postfix 2.5, the default value was 5, but  the  limit  was  not
       actually  enforced.  If	you have set this to a lower non-default value, certificates with
       longer trust chains may now fail to verify. Certificate chains with 1 or 2 CAs are common,
       deeper chains are more rare and any number between 5 and 9 should suffice in practice. You
       can choose a lower number if, for example, you trust certificates directly  signed  by  an
       issuing CA but not any CAs it delegates to.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_cert_file (default: empty)
       File  with the Postfix SMTP server RSA certificate in PEM format.  This file may also con-
       tain the Postfix SMTP server private RSA key.

       Public Internet MX hosts without certificates signed by a "reputable"  CA  must	generate,
       and  be	prepared  to present to most clients, a self-signed or private-CA signed certifi-
       cate. The client will not be able to authenticate the server, but  unless  it  is  running
       Postfix 2.3 or similar software, it will still insist on a server certificate.

       For  servers  that  are	not public Internet MX hosts, Postfix 2.3 supports configurations
       with no certificates. This entails the use of just the anonymous TLS  ciphers,  which  are
       not  supported  by typical SMTP clients. Since such clients will not, as a rule, fall back
       to plain text after a TLS handshake failure, the server will be unable  to  receive  email
       from TLS enabled clients. To avoid accidental configurations with no certificates, Postfix
       2.3 enables  certificate-less  operation  only  when  the  administrator  explicitly  sets
       "smtpd_tls_cert_file  = none". This ensures that new Postfix configurations will not acci-
       dentally run with no certificates.

       Both RSA and DSA certificates are supported.  When both types are present, the cipher used
       determines  which  certificate  will be presented to the client.  For Netscape and OpenSSL
       clients without special cipher choices the RSA certificate is preferred.

       To enable a remote SMTP client to verify the Postfix SMTP server certificate, the  issuing
       CA certificates must be made available to the client. You should include the required cer-
       tificates in the server certificate file, the server certificate first, then  the  issuing
       CA(s) (bottom-up order).

       Example:  the  certificate  for "server.example.com" was issued by "intermediate CA" which
       itself  has  a  certificate  of	"root  CA".   Create  the  server.pem  file   with   "cat
       server_cert.pem intermediate_CA.pem root_CA.pem > server.pem".

       If  you	also  want  to verify client certificates issued by these CAs, you can add the CA
       certificates to the smtpd_tls_CAfile, in which case it is not necessary to  have  them  in
       the smtpd_tls_cert_file or smtpd_tls_dcert_file.

       A certificate supplied here must be usable as an SSL server certificate and hence pass the
       "openssl verify -purpose sslserver ..." test.

       Example:

       smtpd_tls_cert_file = /etc/postfix/server.pem

       This feature is available in Postfix 2.2 and later.

smtpd_tls_cipherlist (default: empty)
       Obsolete Postfix < 2.3 control for the Postfix SMTP server TLS cipher list. It is easy  to
       create inter-operability problems by choosing a non-default cipher list. Do not use a non-
       default TLS cipherlist for MX hosts on the public Internet. Clients  that  begin  the  TLS
       handshake,  but	are unable to agree on a common cipher, may not be able to send any email
       to the SMTP server. Using a restricted cipher list may be more appropriate for a dedicated
       MSA  or	an  internal  mailhub, where one can exert some control over the TLS software and
       settings of the connecting clients.

       Note: do not use "" quotes around the parameter value.

       This feature is available with Postfix version 2.2. It is not used with	Postfix  2.3  and
       later; use smtpd_tls_mandatory_ciphers instead.

smtpd_tls_ciphers (default: export)
       The  minimum TLS cipher grade that the Postfix SMTP server will use with opportunistic TLS
       encryption. Cipher types listed in smtpd_tls_exclude_ciphers are excluded  from	the  base
       definition of the selected cipher grade. The default value "export" ensures maximum inter-
       operability. Because encryption is optional, stronger controls are  not	appropriate,  and
       this setting SHOULD NOT be changed unless the change is essential.

       When  TLS is mandatory the cipher grade is chosen via the smtpd_tls_mandatory_ciphers con-
       figuration parameter, see there for syntax details.

       Example:
       smtpd_tls_ciphers = export

       This feature is available in Postfix 2.6 and later. With earlier Postfix releases only the
       smtpd_tls_mandatory_ciphers  parameter  is  implemented, and opportunistic TLS always uses
       "export" or better (i.e. all) ciphers.

smtpd_tls_dcert_file (default: empty)
       File with the Postfix SMTP server DSA certificate in PEM format.  This file may also  con-
       tain the Postfix SMTP server private DSA key.

       See the discussion under smtpd_tls_cert_file for more details.

       Example:

       smtpd_tls_dcert_file = /etc/postfix/server-dsa.pem

       This feature is available in Postfix 2.2 and later.

smtpd_tls_dh1024_param_file (default: empty)
       File with DH parameters that the Postfix SMTP server should use with EDH ciphers.

       Instead	of using the exact same parameter sets as distributed with other TLS packages, it
       is more secure to generate your own set of parameters with something  like  the	following
       command:

	   openssl gendh -out /etc/postfix/dh_1024.pem -2 1024

       Your  actual source for entropy may differ. Some systems have /dev/random; on other system
       you may consider using the "Entropy Gathering Daemon EGD", available at http://egd.source-
       forge.net/

       Example:

       smtpd_tls_dh1024_param_file = /etc/postfix/dh_1024.pem

       This feature is available with Postfix version 2.2.

smtpd_tls_dh512_param_file (default: empty)
       File with DH parameters that the Postfix SMTP server should use with EDH ciphers.

       See also the discussion under the smtpd_tls_dh1024_param_file configuration parameter.

       Example:

       smtpd_tls_dh512_param_file = /etc/postfix/dh_512.pem

       This feature is available with Postfix version 2.2.

smtpd_tls_dkey_file (default: $smtpd_tls_dcert_file)
       File  with  the	Postfix SMTP server DSA private key in PEM format.  This file may be com-
       bined   with   the   Postfix   SMTP   server   DSA   certificate   file	 specified   with
       $smtpd_tls_dcert_file.

       The  private  key must be accessible without a pass-phrase, i.e. it must not be encrypted.
       File permissions should grant read-only access to the system superuser  account	("root"),
       and no access to anyone else.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_eccert_file (default: empty)
       File  with  the	Postfix  SMTP server ECDSA certificate in PEM format.  This file may also
       contain the Postfix SMTP server private ECDSA key.

       See the discussion under smtpd_tls_cert_file for more details.

       Example:

       smtpd_tls_eccert_file = /etc/postfix/ecdsa-scert.pem

       This feature is available in Postfix 2.6 and later, when Postfix is  compiled  and  linked
       with OpenSSL 1.0.0 or later.

smtpd_tls_eckey_file (default: $smtpd_tls_eccert_file)
       File  with the Postfix SMTP server ECDSA private key in PEM format.  This file may be com-
       bined  with  the   Postfix   SMTP   server   ECDSA   certificate   file	 specified   with
       $smtpd_tls_eccert_file.

       The  private  key must be accessible without a pass-phrase, i.e. it must not be encrypted.
       File permissions should grant read-only access to the system superuser  account	("root"),
       and no access to anyone else.

       This  feature  is  available in Postfix 2.6 and later, when Postfix is compiled and linked
       with OpenSSL 1.0.0 or later.

smtpd_tls_eecdh_grade (default: see postconf -d output)
       The Postfix SMTP server security grade for ephemeral elliptic-curve Diffie-Hellman (EECDH)
       key exchange.

       The available choices are:

       none   Don't  use EECDH. Ciphers based on EECDH key exchange will be disabled. This is the
	      default in Postfix versions 2.6 and 2.7.

       strong Use EECDH with approximately 128 bits of security  at  a	reasonable  computational
	      cost.  This  is  the  current best-practice trade-off between security and computa-
	      tional efficiency. This is the default in Postfix version 2.8 and later.

       ultra  Use EECDH with approximately 192 bits of security at  computational  cost  that  is
	      approximately  twice  as high as 128 bit strength ECC. Barring significant progress
	      in attacks on elliptic curve crypto-systems, the "strong" curve is  sufficient  for
	      most users.

       This  feature  is  available in Postfix 2.6 and later, when it is compiled and linked with
       OpenSSL 1.0.0 or later.

smtpd_tls_exclude_ciphers (default: empty)
       List of ciphers or cipher types to exclude from the SMTP server cipher  list  at  all  TLS
       security  levels.  Excluding  valid  ciphers  can create interoperability problems. DO NOT
       exclude ciphers unless it is essential to do so. This is not an OpenSSL cipherlist; it  is
       a  simple list separated by whitespace and/or commas. The elements are a single cipher, or
       one or more "+" separated cipher properties, in which case only ciphers matching  all  the
       properties are excluded.

       Examples (some of these will cause problems):

	   smtpd_tls_exclude_ciphers = aNULL
	   smtpd_tls_exclude_ciphers = MD5, DES
	   smtpd_tls_exclude_ciphers = DES+MD5
	   smtpd_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
	   smtpd_tls_exclude_ciphers = kEDH+aRSA

       The  first  setting disables anonymous ciphers. The next setting disables ciphers that use
       the MD5 digest algorithm or the (single) DES encryption algorithm. The next  setting  dis-
       ables  ciphers  that  use MD5 and DES together.	The next setting disables the two ciphers
       "AES256-SHA" and "DES-CBC3-MD5". The last setting disables  ciphers  that  use  "EDH"  key
       exchange with RSA authentication.

       This feature is available in Postfix 2.3 and later.

smtpd_tls_fingerprint_digest (default: md5)
       The  message  digest  algorithm	used  to  construct  client-certificate  fingerprints for
       check_ccert_access and permit_tls_clientcerts. The default algorithm is md5, for backwards
       compatibility with Postfix releases prior to 2.5.

       The  best  practice  algorithm is now sha1. Recent advances in hash function cryptanalysis
       have led to md5 being deprecated in favor of sha1.  However, as long as there are no known
       "second	pre-image"  attacks  against md5, its use in this context can still be considered
       safe.

       While additional digest algorithms are often  available	with  OpenSSL's  libcrypto,  only
       those  used  by	libssl	in SSL cipher suites are available to Postfix. For now this means
       just md5 or sha1.

       To find the fingerprint of a specific certificate file, with a specific digest  algorithm,
       run:

	   $ openssl x509 -noout -fingerprint -digest -in certfile.pem

       The text to the right of "=" sign is the desired fingerprint.  For example:

	   $ openssl x509 -noout -fingerprint -sha1 -in cert.pem
	   SHA1 Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A

       Example: client-certificate access table, with sha1 fingerprints:

	   /etc/postfix/main.cf:
	       smtpd_tls_fingerprint_digest = sha1
	       smtpd_client_restrictions =
		   check_ccert_access hash:/etc/postfix/access,
		   reject
	   /etc/postfix/access:
	       # Action folded to next line...
	       AF:88:7C:AD:51:95:6F:36:96:F6:01:FB:2E:48:CD:AB:49:25:A2:3B
		   OK
	       85:16:78:FD:73:6E:CE:70:E0:31:5F:0D:3C:C8:6D:C4:2C:24:59:E1
		   permit_auth_destination

       This feature is available in Postfix 2.5 and later.

smtpd_tls_key_file (default: $smtpd_tls_cert_file)
       File  with  the	Postfix SMTP server RSA private key in PEM format.  This file may be com-
       bined   with   the   Postfix   SMTP   server   RSA   certificate   file	 specified   with
       $smtpd_tls_cert_file.

       The  private  key must be accessible without a pass-phrase, i.e. it must not be encrypted.
       File permissions should grant read-only access to the system superuser  account	("root"),
       and no access to anyone else.

smtpd_tls_loglevel (default: 0)
       Enable  additional  Postfix  SMTP server logging of TLS activity.  Each logging level also
       includes the information that is logged at a lower logging level.

	      0 Disable logging of TLS activity.

	      1 Log TLS handshake and certificate information.

	      2 Log levels during TLS negotiation.

	      3 Log hexadecimal and ASCII dump of TLS negotiation process.

	      4 Also log hexadecimal and ASCII dump of complete transmission after STARTTLS.

       Use "smtpd_tls_loglevel = 3" only in case of problems. Use of loglevel 4 is strongly  dis-
       couraged.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_mandatory_ciphers (default: medium)
       The  minimum  TLS  cipher  grade  that the Postfix SMTP server will use with mandatory TLS
       encryption. The default grade ("medium") is sufficiently  strong  that  any  benefit  from
       globally  restricting  TLS  sessions to a more stringent grade is likely negligible, espe-
       cially given the fact that many implementations still do not offer  any	stronger  ("high"
       grade) ciphers, while those that do, will always use "high" grade ciphers. So insisting on
       "high" grade ciphers is generally counter-productive. Allowing "export" or  "low"  ciphers
       is  typically  not  a  good idea, as systems limited to just these are limited to obsolete
       browsers. No known SMTP clients fail to support at least  one  "medium"	or  "high"  grade
       cipher.

       The following cipher grades are supported:

       export Enable  "EXPORT"	grade  or stronger OpenSSL ciphers.  This is the most appropriate
	      setting for public MX hosts, and is always used with opportunistic TLS  encryption.
	      The  underlying cipherlist is specified via the tls_export_cipherlist configuration
	      parameter, which you are strongly encouraged to not change.

       low    Enable "LOW" grade or stronger OpenSSL ciphers. The underlying cipherlist is speci-
	      fied  via  the  tls_low_cipherlist  configuration parameter, which you are strongly
	      encouraged to not change.

       medium Enable "MEDIUM" grade or stronger OpenSSL ciphers. These use 128-bit or longer sym-
	      metric bulk-encryption keys. This is the default minimum strength for mandatory TLS
	      encryption. The underlying cipherlist is specified  via  the  tls_medium_cipherlist
	      configuration parameter, which you are strongly encouraged to not change.

       high   Enable  only  "HIGH"  grade OpenSSL ciphers. The underlying cipherlist is specified
	      via the tls_high_cipherlist configuration parameter, which you are strongly encour-
	      aged to not change.

       null   Enable  only  the  "NULL"  OpenSSL  ciphers,  these  provide authentication without
	      encryption.  This setting is only appropriate in the rare case that all clients are
	      prepared	to use NULL ciphers (not normally enabled in TLS clients). The underlying
	      cipherlist is specified via the tls_null_cipherlist configuration parameter,  which
	      you are strongly encouraged to not change.

       Cipher  types  listed  in smtpd_tls_mandatory_exclude_ciphers or smtpd_tls_exclude_ciphers
       are excluded from the base definition of the selected cipher grade. See	smtpd_tls_ciphers
       for cipher controls that apply to opportunistic TLS.

       The  underlying	cipherlists  for  grades other than "null" include anonymous ciphers, but
       these are automatically filtered out if the server is configured to ask	for  client  cer-
       tificates.   You are very unlikely to need to take any steps to exclude anonymous ciphers,
       they are excluded automatically as required.  If you must exclude anonymous  ciphers  even
       when  Postfix  does  not  need  or use peer certificates, set "smtpd_tls_exclude_ciphers =
       aNULL". To exclude anonymous ciphers only when  TLS  is	enforced,  set	"smtpd_tls_manda-
       tory_exclude_ciphers = aNULL".

       This feature is available in Postfix 2.3 and later.

smtpd_tls_mandatory_exclude_ciphers (default: empty)
       Additional  list of ciphers or cipher types to exclude from the SMTP server cipher list at
       mandatory TLS security levels. This list works in addition to the exclusions  listed  with
       smtpd_tls_exclude_ciphers (see there for syntax details).

       This feature is available in Postfix 2.3 and later.

smtpd_tls_mandatory_protocols (default: !SSLv2)
       The  SSL/TLS  protocols accepted by the Postfix SMTP server with mandatory TLS encryption.
       If the list is empty, the server supports all available SSL/TLS protocol versions.  A non-
       empty  value  is  a  list of protocol names separated by whitespace, commas or colons. The
       supported protocol names are "SSLv2", "SSLv3" and "TLSv1", and are not case sensitive.

       Note: As of OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1" and  "TLSv1.2".  If  an
       older  Postfix  version	is linked against OpenSSL 1.0.1 or later, these, or any other new
       protocol versions, are unconditionally enabled.

       With Postfix >= 2.5 the parameter syntax is expanded to support protocol  exclusions.  One
       can  now  explicitly exclude SSLv2 by setting "smtpd_tls_mandatory_protocols = !SSLv2". To
       exclude both SSLv2 and SSLv3 set "smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3". Listing
       the  protocols  to include, rather than protocols to exclude, is supported, but not recom-
       mended. The exclusion form more closely matches the behaviour when the OpenSSL library  is
       newer than Postfix.

       Since  SSL version 2 has known protocol weaknesses and is now deprecated, the default set-
       ting excludes "SSLv2".  This means that by default, SSL version 2 will not be used at  the
       "encrypt" security level.

       Example:

       smtpd_tls_mandatory_protocols = TLSv1
       # Alternative form with Postfix >= 2.5:
       smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3

       This feature is available in Postfix 2.3 and later.

smtpd_tls_protocols (default: empty)
       List  of  TLS  protocols  that the Postfix SMTP server will exclude or include with oppor-
       tunistic TLS encryption. This parameter SHOULD be left at its default empty value,  allow-
       ing all protocols to be used with opportunistic TLS.

       In  main.cf the values are separated by whitespace, commas or colons. An empty value means
       allow all protocols. The valid protocol names, (see \fBfBSSL_get_version(3)), are "SSLv2",
       "SSLv3"	and  "TLSv1". In smtp_tls_policy_maps table entries, "protocols" attribute values
       are separated by a colon.

       Note: As of OpenSSL 1.0.1 two new protocols are defined, "TLSv1.1" and  "TLSv1.2".  If  an
       older  Postfix  version	is linked against OpenSSL 1.0.1 or later, these, or any other new
       protocol versions, are unconditionally enabled.

       To include a protocol list its name, to exclude it, prefix the name with a "!"  character.
       To exclude SSLv2 even for opportunistic TLS set "smtpd_tls_protocols = !SSLv2". To exclude
       both "SSLv2" and "SSLv3" set "smtpd_tls_protocols = !SSLv2,  !SSLv3".  Explicitly  listing
       the  protocols  to include, rather than protocols to exclude, is supported, but not recom-
       mended.	The exclusion form more closely matches the behaviour when the OpenSSL library is
       newer than Postfix.

       Example:
       smtpd_tls_protocols = !SSLv2

       This feature is available in Postfix 2.6 and later.

smtpd_tls_received_header (default: no)
       Request	that  the  Postfix  SMTP  server produces Received:  message headers that include
       information about the protocol and cipher used, as  well  as  the  client  CommonName  and
       client certificate issuer CommonName.  This is disabled by default, as the information may
       be modified in transit through other mail servers.  Only information that was recorded  by
       the final destination can be trusted.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_req_ccert (default: no)
       With  mandatory	TLS encryption, require a trusted remote SMTP client certificate in order
       to allow TLS connections to proceed.  This option implies "smtpd_tls_ask_ccert = yes".

       When TLS encryption is optional, this setting is ignored with a	warning  written  to  the
       mail log.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_security_level (default: empty)
       The  SMTP TLS security level for the Postfix SMTP server; when a non-empty value is speci-
       fied, this overrides the obsolete parameters  smtpd_use_tls  and  smtpd_enforce_tls.  This
       parameter is ignored with "smtpd_tls_wrappermode = yes".

       Specify one of the following security levels:

       none   TLS will not be used.

       may    Opportunistic  TLS:  announce  STARTTLS support to SMTP clients, but do not require
	      that clients use TLS encryption.

       encrypt
	      Mandatory TLS encryption: announce STARTTLS support to SMTP  clients,  and  require
	      that  clients use TLS encryption. According to RFC 2487 this MUST NOT be applied in
	      case of a publicly-referenced SMTP server. Instead, this option should be used only
	      on dedicated servers.

       Note 1: the "fingerprint", "verify" and "secure" levels are not supported here.	The Post-
       fix SMTP server logs a warning and uses "encrypt" instead.  To verify SMTP client certifi-
       cates,  see  TLS_README	for a discussion of the smtpd_tls_ask_ccert, smtpd_tls_req_ccert,
       and permit_tls_clientcerts features.

       Note   2:   The	 parameter   setting   "smtpd_tls_security_level   =   encrypt"   implies
       "smtpd_tls_auth_only = yes".

       Note 3: when invoked via "sendmail -bs", Postfix will never offer STARTTLS due to insuffi-
       cient privileges to access the server private key. This is intended behavior.

       This feature is available in Postfix 2.3 and later.

smtpd_tls_session_cache_database (default: empty)
       Name of the file containing the optional Postfix SMTP server TLS session cache. Specify	a
       database  type  that supports enumeration, such as btree or sdbm; there is no need to sup-
       port concurrent access.	The file is created if it does not  exist.  The  smtpd(8)  daemon
       does  not  use  this parameter directly, rather the cache is implemented indirectly in the
       tlsmgr(8) daemon. This means that per-smtpd-instance master.cf overrides of this parameter
       are  not  effective. Note, that each of the cache databases supported by tlsmgr(8) daemon:
       $smtpd_tls_session_cache_database, $smtp_tls_session_cache_database (and with Postfix  2.3
       and  later  $lmtp_tls_session_cache_database), needs to be stored separately. It is not at
       this time possible to store multiple caches in a single database.

       Note: dbm databases are not suitable. TLS session objects are too large.

       As of version 2.5, Postfix no longer uses root privileges when opening this file. The file
       should  now  be	stored	under  the  Postfix-owned  data_directory. As a migration aid, an
       attempt to open the file under a non-Postfix directory is redirected to the  Postfix-owned
       data_directory, and a warning is logged.

       Example:

       smtpd_tls_session_cache_database = btree:/var/db/postfix/smtpd_scache

       This feature is available in Postfix 2.2 and later.

smtpd_tls_session_cache_timeout (default: 3600s)
       The  expiration time of Postfix SMTP server TLS session cache information. A cache cleanup
       is  performed  periodically  every  $smtpd_tls_session_cache_timeout  seconds.	As   with
       $smtpd_tls_session_cache_database,  this  parameter is implemented in the tlsmgr(8) daemon
       and therefore per-smtpd-instance master.cf overrides are not possible.

       This feature is available in Postfix 2.2 and later.

smtpd_tls_wrappermode (default: no)
       Run the Postfix SMTP server in the non-standard	"wrapper"  mode,  instead  of  using  the
       STARTTLS command.

       If  you	want to support this service, enable a special port in master.cf, and specify "-o
       smtpd_tls_wrappermode=yes" on the SMTP server's command line. Port 465  (smtps)	was  once
       chosen for this purpose.

       This feature is available in Postfix 2.2 and later.

smtpd_use_tls (default: no)
       Opportunistic  TLS:  announce  STARTTLS	support  to SMTP clients, but do not require that
       clients use TLS encryption.

       Note: when invoked via "sendmail -bs", Postfix will never offer STARTTLS due  to  insuffi-
       cient privileges to access the server private key. This is intended behavior.

       This  feature  is  available  in  Postfix  2.2  and  later. With Postfix 2.3 and later use
       smtpd_tls_security_level instead.

soft_bounce (default: no)
       Safety net to keep mail queued that would otherwise  be	returned  to  the  sender.   This
       parameter  disables  locally-generated  bounces, and prevents the Postfix SMTP server from
       rejecting mail permanently, by changing 5xx reply codes into 4xx.  However, soft_bounce is
       no cure for address rewriting mistakes or mail routing mistakes.

       Example:

       soft_bounce = yes

stale_lock_time (default: 500s)
       The  time  after  which	a  stale exclusive mailbox lockfile is removed.  This is used for
       delivery to file or mailbox.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

stress (default: empty)
       This feature is documented in the STRESS_README document.

       This feature is available in Postfix 2.5 and later.

strict_7bit_headers (default: no)
       Reject  mail  with  8-bit  text	in  message headers. This blocks mail from poorly written
       applications.

       This feature should not be enabled on a general purpose mail server, because it is  likely
       to reject legitimate email.

       This feature is available in Postfix 2.0 and later.

strict_8bitmime (default: no)
       Enable both strict_7bit_headers and strict_8bitmime_body.

       This  feature should not be enabled on a general purpose mail server, because it is likely
       to reject legitimate email.

       This feature is available in Postfix 2.0 and later.

strict_8bitmime_body (default: no)
       Reject 8-bit message body text without 8-bit  MIME  content  encoding  information.   This
       blocks mail from poorly written applications.

       Unfortunately,  this  also  rejects  majordomo approval requests when the included request
       contains valid 8-bit MIME mail, and it rejects bounces  from  mailers  that  do	not  MIME
       encapsulate  8-bit  content (for example, bounces from qmail or from old versions of Post-
       fix).

       This feature should not be enabled on a general purpose mail server, because it is  likely
       to reject legitimate email.

       This feature is available in Postfix 2.0 and later.

strict_mailbox_ownership (default: yes)
       Defer  delivery when a mailbox file is not owned by its recipient.  The default setting is
       not backwards compatible.

       This feature is available in Postfix 2.5.3 and later.

strict_mime_encoding_domain (default: no)
       Reject mail with invalid Content-Transfer-Encoding: information for the message/* or  mul-
       tipart/* MIME content types.  This blocks mail from poorly written software.

       This  feature  should  not  be  enabled	on a general purpose mail server, because it will
       reject mail after a single violation.

       This feature is available in Postfix 2.0 and later.

strict_rfc821_envelopes (default: no)
       Require that addresses received in SMTP MAIL FROM and RCPT TO commands are  enclosed  with
       <>, and that those addresses do not contain RFC 822 style comments or phrases.  This stops
       mail from poorly written software.

       By default, the Postfix SMTP server accepts RFC 822  syntax  in	MAIL  FROM  and  RCPT  TO
       addresses.

sun_mailtool_compatibility (default: no)
       Obsolete  SUN  mailtool	compatibility feature. Instead, use "mailbox_delivery_lock = dot-
       lock".

swap_bangpath (default: yes)
       Enable the rewriting of "site!user" into "user@site".  This is necessary if  your  machine
       is connected to UUCP networks.  It is enabled by default.

       Note:  with Postfix version 2.2, message header address rewriting happens only when one of
       the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received  from  a	network  client  that  matches	$local_header_re-
	      write_clients,

       o      The  message  is	received  from	the network, and the remote_header_rewrite_domain
	      parameter specifies a non-empty value.

       To get the behavior before Postfix version 2.2,	specify  "local_header_rewrite_clients	=
       static:all".

       Example:

       swap_bangpath = no

syslog_facility (default: mail)
       The  syslog  facility of Postfix logging. Specify a facility as defined in syslog.conf(5).
       The default facility is "mail".

       Warning: a non-default syslog_facility setting takes effect only after a  Postfix  process
       has  completed  initialization.	 Errors during process initialization will be logged with
       the default facility.  Examples are errors while parsing the command line  arguments,  and
       errors while accessing the Postfix main.cf configuration file.

syslog_name (default: see postconf -d output)
       The  mail  system  name	that  is prepended to the process name in syslog records, so that
       "smtpd" becomes, for example, "postfix/smtpd".

       Warning: a non-default syslog_name setting takes effect only after a Postfix  process  has
       completed  initialization.  Errors  during  process initialization will be logged with the
       default name. Examples are errors while parsing the command  line  arguments,  and  errors
       while accessing the Postfix main.cf configuration file.

tcp_windowsize (default: 0)
       An optional workaround for routers that break TCP window scaling.  Specify a value > 0 and
       < 65536 to enable this feature.	With Postfix TCP servers (smtpd(8), qmqpd(8)), this  fea-
       ture is implemented by the Postfix master(8) daemon.

       To change this parameter without stopping Postfix, you need to first terminate all Postfix
       TCP servers:

	   # postconf -e master_service_disable=inet
	   # postfix reload

       This immediately terminates all processes that  accept  network	connections.   Next,  you
       enable Postfix TCP servers with the updated tcp_windowsize setting:

	   # postconf -e tcp_windowsize=65535 master_service_disable=
	   # postfix reload

       If you skip these steps with a running Postfix system, then the tcp_windowsize change will
       work only for Postfix TCP clients (smtp(8), lmtp(8)).

       This feature is available in Postfix 2.6 and later.

tls_append_default_CA (default: no)
       Append the system-supplied default certificate authority certificates to the  ones  speci-
       fied  with  *_tls_CApath or *_tls_CAfile.  The default is "no"; this prevents Postfix from
       trusting  third-party  certificates  and  giving   them	 relay	 permission   with   per-
       mit_tls_all_clientcerts.

       This  feature  is  available  in  Postfix 2.4.15, 2.5.11, 2.6.8, 2.7.2 and later versions.
       Specify "tls_append_default_CA = yes" for backwards compatibility, to avoid breaking  cer-
       tificate verification with sites that don't use permit_tls_all_clientcerts.

tls_daemon_random_bytes (default: 32)
       The  number  of	pseudo-random bytes that an smtp(8) or smtpd(8) process requests from the
       tlsmgr(8) server in order to seed its internal pseudo random number generator (PRNG).  The
       default	of  32	bytes  (equivalent  to	256  bits) is sufficient to generate a 128bit (or
       168bit) session key.

       This feature is available in Postfix 2.2 and later.

tls_disable_workarounds (default: see postconf -d output)
       List or bit-mask of OpenSSL bug work-arounds to disable.

       The OpenSSL toolkit includes a set of  work-arounds  for  buggy	SSL/TLS  implementations.
       Applications,  such  as	Postfix,  that	want to maximize interoperability ask the OpenSSL
       library to enable the full set of recommended work-arounds.

       From time to time, it is discovered that a  work-around	creates  a  security  issue,  and
       should  no  longer be used. If upgrading OpenSSL to a fixed version is not an option or an
       upgrade is not available in a timely manner, or in  closed  environments  where	no  buggy
       clients	or  servers  exist,  it  may be appropriate to disable some or all of the OpenSSL
       interoperability work-arounds. This parameter specifies which bug work-arounds to disable.

       If the value of the parameter is a hexadecimal long integer starting with  "0x",  the  bug
       work-arounds  corresponding  to	the  bits  specified  in  its  value are removed from the
       SSL_OP_ALL work-around bit-mask (see openssl/ssl.h and  SSL_CTX_set_options(3)).  You  can
       specify	more  bits  than  are  present in SSL_OP_ALL, excess bits are ignored. Specifying
       0xFFFFFFFF disables all bug-workarounds on a 32-bit system. This should also be sufficient
       on  64-bit systems, until OpenSSL abandons support for 32-bit systems and starts using the
       high 32 bits of a 64-bit bug-workaround mask.

       Otherwise, the parameter is a white-space or comma separated list of  specific  named  bug
       work-arounds chosen from the list below. It is possible that your OpenSSL version includes
       new bug work-arounds added after your Postfix source code was last updated, in  that  case
       you can only disable one of these via the hexadecimal syntax above.

       MICROSOFT_SESS_ID_BUG
	      See SSL_CTX_set_options(3)

       NETSCAPE_CHALLENGE_BUG
	      See SSL_CTX_set_options(3)

       LEGACY_SERVER_CONNECT
	      See SSL_CTX_set_options(3)

       NETSCAPE_REUSE_CIPHER_CHANGE_BUG
	      also  aliased  as  CVE-2010-4180.  Postfix 2.8 disables this work-around by default
	      with OpenSSL versions that may predate the fix. Fixed in OpenSSL 0.9.8q and OpenSSL
	      1.0.0c.

       SSLREF2_REUSE_CERT_TYPE_BUG
	      See SSL_CTX_set_options(3)

       MICROSOFT_BIG_SSLV3_BUFFER
	      See SSL_CTX_set_options(3)

       MSIE_SSLV2_RSA_PADDING
	      also  aliased  as  CVE-2005-2969.  Postfix 2.8 disables this work-around by default
	      with OpenSSL versions that may predate the fix. Fixed in OpenSSL 0.9.7h and OpenSSL
	      0.9.8a.

       SSLEAY_080_CLIENT_DH_BUG
	      See SSL_CTX_set_options(3)

       TLS_D5_BUG
	      See SSL_CTX_set_options(3)

       TLS_BLOCK_PADDING_BUG
	      See SSL_CTX_set_options(3)

       TLS_ROLLBACK_BUG
	      See  SSL_CTX_set_options(3).   This  is disabled in OpenSSL 0.9.7 and later. Nobody
	      should still be using 0.9.6!

       DONT_INSERT_EMPTY_FRAGMENTS
	      See SSL_CTX_set_options(3)

       CRYPTOPRO_TLSEXT_BUG
	      New with GOST support in OpenSSL 1.0.0.

       This feature is available in Postfix 2.8 and later.

tls_eecdh_strong_curve (default: prime256v1)
       The elliptic curve used by  the	SMTP  server  for  sensibly  strong  ephemeral	ECDH  key
       exchange.  This	curve  is  used  by the Postfix SMTP server when "smtpd_tls_eecdh_grade =
       strong". The phrase "sensibly strong" means approximately 128-bit security based  on  best
       known  attacks.	The  selected  curve  must  be	implemented  by  OpenSSL  (as reported by
       ecparam(1) with the "-list_curves" option) and be one of  the  curves  listed  in  Section
       5.1.1 of RFC 4492. You should not generally change this setting.

       This    default	  curve    is	 specified   in   NSA	"Suite	 B"   Cryptography   (see
       http://www.nsa.gov/ia/industry/crypto_suite_b.cfm) for information classified as SECRET.

       Note: elliptic curve names are poorly standardized; different standards groups are assign-
       ing  different  names  to  the  same  underlying  curves.   The	curve with the X9.62 name
       "prime256v1" is also known under the SECG name "secp256r1", but OpenSSL does not recognize
       the latter name.

       This  feature  is  available in Postfix 2.6 and later, when it is compiled and linked with
       OpenSSL 1.0.0 or later.

tls_eecdh_ultra_curve (default: secp384r1)
       The elliptic curve used by the  SMTP  server  for  maximally  strong  ephemeral	ECDH  key
       exchange.  This	curve  is  used  by the Postfix SMTP server when "smtpd_tls_eecdh_grade =
       ultra". The phrase "maximally strong" means approximately 192-bit security based  on  best
       known  attacks.	 This additional strength comes at a significant computational cost, most
       users should instead set "smtpd_tls_eecdh_grade = strong".  The	selected  curve  must  be
       implemented  by	OpenSSL (as reported by ecparam(1) with the "-list_curves" option) and be
       one of the curves listed in Section 5.1.1 of RFC 4492. You  should  not	generally  change
       this setting.

       This   default	"ultra"   curve   is   specified  in  NSA  "Suite  B"  Cryptography  (see
       http://www.nsa.gov/ia/industry/crypto_suite_b.cfm)  for	information  classified  as   TOP
       SECRET.

       This  feature  is  available in Postfix 2.6 and later, when it is compiled and linked with
       OpenSSL 1.0.0 or later.

tls_export_cipherlist (default: ALL:+RC4:@STRENGTH)
       The OpenSSL cipherlist for "EXPORT" or higher grade ciphers. This defines the  meaning  of
       the   "export"  setting	in  smtpd_tls_mandatory_ciphers,  smtp_tls_mandatory_ciphers  and
       lmtp_tls_mandatory_ciphers. This is the	cipherlist  for  the  opportunistic  ("may")  TLS
       client  security level and is the default cipherlist for the SMTP server. You are strongly
       encouraged to not change this setting. With OpenSSL 1.0.0 and  later  the  cipherlist  may
       start  with  an "aNULL:" prefix, which restores the 0.9.8-compatible ordering of the aNULL
       ciphers to the top of the list when they are enabled. This prefix is not needed with  pre-
       vious OpenSSL releases.

       This feature is available in Postfix 2.3 and later.

tls_high_cipherlist (default: ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
       The  OpenSSL  cipherlist  for "HIGH" grade ciphers. This defines the meaning of the "high"
       setting in  smtpd_tls_mandatory_ciphers,  smtp_tls_mandatory_ciphers  and  lmtp_tls_manda-
       tory_ciphers.  You  are strongly encouraged to not change this setting. With OpenSSL 1.0.0
       and later the cipherlist may start with an "aNULL:" prefix, which restores the  0.9.8-com-
       patible	ordering  of the aNULL ciphers to the top of the list when they are enabled. This
       prefix is not needed with previous OpenSSL releases.

       This feature is available in Postfix 2.3 and later.

tls_low_cipherlist (default: ALL:!EXPORT:+RC4:@STRENGTH)
       The OpenSSL cipherlist for "LOW" or higher grade ciphers. This defines the meaning of  the
       "low"	setting    in	 smtpd_tls_mandatory_ciphers,	 smtp_tls_mandatory_ciphers   and
       lmtp_tls_mandatory_ciphers. You are strongly encouraged to not change this setting.   With
       OpenSSL	1.0.0  and later the cipherlist may start with an "aNULL:" prefix, which restores
       the 0.9.8-compatible ordering of the aNULL ciphers to the top of the list  when	they  are
       enabled. This prefix is not needed with previous OpenSSL releases.

       This feature is available in Postfix 2.3 and later.

tls_medium_cipherlist (default: ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
       The  OpenSSL  cipherlist for "MEDIUM" or higher grade ciphers. This defines the meaning of
       the  "medium"  setting  in  smtpd_tls_mandatory_ciphers,  smtp_tls_mandatory_ciphers   and
       lmtp_tls_mandatory_ciphers. This is the default cipherlist for mandatory TLS encryption in
       the TLS client (with anonymous ciphers disabled when verifying server  certificates).  You
       are  strongly  encouraged  to  not  change this setting.  With OpenSSL 1.0.0 and later the
       cipherlist may start with an "aNULL:" prefix, which restores the 0.9.8-compatible ordering
       of  the	aNULL  ciphers	to  the top of the list when they are enabled. This prefix is not
       needed with previous OpenSSL releases.

       This feature is available in Postfix 2.3 and later.

tls_null_cipherlist (default: eNULL:!aNULL)
       The OpenSSL cipherlist for  "NULL"  grade  ciphers  that  provide  authentication  without
       encryption. This defines the meaning of the "null" setting in smtpd_mandatory_tls_ciphers,
       smtp_tls_mandatory_ciphers and lmtp_tls_mandatory_ciphers.  You are strongly encouraged to
       not change this setting.

       This feature is available in Postfix 2.3 and later.

tls_preempt_cipherlist (default: no)
       With  SSLv3  and  later,  use the server's cipher preference order instead of the client's
       cipher preference order.

       By default, the OpenSSL server selects the client's most preferred cipher that the  server
       supports.  With	SSLv3 and later, the server may choose its own most preferred cipher that
       is supported (offered) by the  client.  Setting	"tls_preempt_cipherlist  =  yes"  enables
       server cipher preferences.

       While server cipher selection may in some cases lead to a more secure or performant cipher
       choice, there is some risk of interoperability issues. In the past, some SSL clients  have
       listed lower priority ciphers that they did not implement correctly. If the server chooses
       a cipher that the client prefers less, it may select a cipher whose client  implementation
       is flawed.

       This  feature is available in Postfix 2.8 and later, in combination with OpenSSL 0.9.7 and
       later.

tls_random_bytes (default: 32)
       The number of bytes that tlsmgr(8) reads from $tls_random_source when (re)seeding the  in-
       memory  pseudo  random number generator (PRNG) pool. The default of 32 bytes (256 bits) is
       good enough for 128bit symmetric keys.  If using EGD or a device file, a  maximum  of  255
       bytes is read.

       This feature is available in Postfix 2.2 and later.

tls_random_exchange_name (default: see postconf -d output)
       Name  of  the  pseudo  random  number  generator  (PRNG)  state file that is maintained by
       tlsmgr(8). The file is created when it does not exist, and its length  is  fixed  at  1024
       bytes.

       As  of version 2.5, Postfix no longer uses root privileges when opening this file, and the
       default file location was  changed  from  ${config_directory}/prng_exch	to  ${data_direc-
       tory}/prng_exch.   As  a  migration  aid,  an attempt to open the file under a non-Postfix
       directory is redirected to the Postfix-owned data_directory, and a warning is logged.

       This feature is available in Postfix 2.2 and later.

tls_random_prng_update_period (default: 3600s)
       The time between attempts by tlsmgr(8) to save the state of the pseudo random number  gen-
       erator (PRNG) to the file specified with $tls_random_exchange_name.

       This feature is available in Postfix 2.2 and later.

tls_random_reseed_period (default: 3600s)
       The maximal time between attempts by tlsmgr(8) to re-seed the in-memory pseudo random num-
       ber generator (PRNG) pool from external	sources.   The	actual	time  between  re-seeding
       attempts is calculated using the PRNG, and is between 0 and the time specified.

       This feature is available in Postfix 2.2 and later.

tls_random_source (default: see postconf -d output)
       The  external  entropy  source  for the in-memory tlsmgr(8) pseudo random number generator
       (PRNG) pool. Be sure to specify a non-blocking source.  If this source is  not  a  regular
       file,  the  entropy  source  type must be prepended:  egd:/path/to/egd_socket for a source
       with EGD compatible socket interface, or dev:/path/to/device for a device file.

       Note: on OpenBSD systems specify /dev/arandom when /dev/urandom gives timeout errors.

       This feature is available in Postfix 2.2 and later.

tlsproxy_enforce_tls (default: $smtpd_enforce_tls)
       Mandatory TLS: announce STARTTLS support to SMTP clients, and require that clients use TLS
       encryption. See smtpd_enforce_tls for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_service_name (default: tlsproxy)
       The  name  of  the tlsproxy(8) service entry in master.cf. This service performs plaintext
       <=> TLS ciphertext conversion.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_CAfile (default: $smtpd_tls_CAfile)
       A file containing (PEM format) CA certificates of root CAs trusted to sign  either  remote
       SMTP  client  certificates or intermediate CA certificates.  See smtpd_tls_CAfile for fur-
       ther details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_CApath (default: $smtpd_tls_CApath)
       A directory containing (PEM format) CA certificates of root CAs	trusted  to  sign  either
       remote  SMTP client certificates or intermediate CA certificates. See smtpd_tls_CApath for
       further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_always_issue_session_ids (default: $smtpd_tls_always_issue_session_ids)
       Force the Postfix tlsproxy(8) server to issue a TLS session  id,  even  when  TLS  session
       caching is turned off. See smtpd_tls_always_issue_session_ids for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_ask_ccert (default: $smtpd_tls_ask_ccert)
       Ask  a  remote  SMTP  client for a client certificate. See smtpd_tls_ask_ccert for further
       details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_ccert_verifydepth (default: $smtpd_tls_ccert_verifydepth)
       The verification depth for remote SMTP client certificates. A depth of 1 is sufficient  if
       the  issuing  CA is listed in a local CA file. See smtpd_tls_ccert_verifydepth for further
       details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_cert_file (default: $smtpd_tls_cert_file)
       File with the Postfix tlsproxy(8) server RSA certificate in PEM	format.   This	file  may
       also  contain the Postfix tlsproxy(8) server private RSA key.  See smtpd_tls_cert_file for
       further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_ciphers (default: $smtpd_tls_ciphers)
       The minimum TLS cipher grade that the Postfix tlsproxy(8) server will use with opportunis-
       tic TLS encryption. See smtpd_tls_ciphers for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_dcert_file (default: $smtpd_tls_dcert_file)
       File  with  the	Postfix  tlsproxy(8) server DSA certificate in PEM format.  This file may
       also contain the Postfix tlsproxy(8) server private DSA key.  See smtpd_tls_dcert_file for
       further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_dh1024_param_file (default: $smtpd_tls_dh1024_param_file)
       File  with  DH parameters that the Postfix tlsproxy(8) server should use with EDH ciphers.
       See smtpd_tls_dh1024_param_file for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_dh512_param_file (default: $smtpd_tls_dh512_param_file)
       File with DH parameters that the Postfix tlsproxy(8) server should use with  EDH  ciphers.
       See smtpd_tls_dh512_param_file for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_dkey_file (default: $smtpd_tls_dkey_file)
       File  with the Postfix tlsproxy(8) server DSA private key in PEM format.  This file may be
       combined  with  the  Postfix  tlsproxy(8)  server  DSA  certificate  file  specified  with
       $smtpd_tls_dcert_file.  See smtpd_tls_dkey_file for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_eccert_file (default: $smtpd_tls_eccert_file)
       File  with  the Postfix tlsproxy(8) server ECDSA certificate in PEM format.  This file may
       also contain the Postfix tlsproxy(8) server private ECDSA key.  See  smtpd_tls_eccert_file
       for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_eckey_file (default: $smtpd_tls_eckey_file)
       File  with  the Postfix tlsproxy(8) server ECDSA private key in PEM format.  This file may
       be combined with the Postfix tlsproxy(8) server	ECDSA  certificate  file  specified  with
       $smtpd_tls_eccert_file.	See smtpd_tls_eckey_file for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_eecdh_grade (default: $smtpd_tls_eecdh_grade)
       The  Postfix tlsproxy(8) server security grade for ephemeral elliptic-curve Diffie-Hellman
       (EECDH) key exchange. See smtpd_tls_eecdh_grade for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_exclude_ciphers (default: $smtpd_tls_exclude_ciphers)
       List of ciphers or cipher types to exclude from the tlsproxy(8) server cipher list at  all
       TLS security levels. See smtpd_tls_exclude_ciphers for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_fingerprint_digest (default: $smtpd_tls_fingerprint_digest)
       The  message  digest  algorithm	used  to  construct  client-certificate fingerprints. See
       smtpd_tls_fingerprint_digest for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_key_file (default: $smtpd_tls_key_file)
       File with the Postfix tlsproxy(8) server RSA private key in PEM format.	This file may  be
       combined  with  the  Postfix  tlsproxy(8)  server  RSA  certificate  file  specified  with
       $smtpd_tls_cert_file.  See smtpd_tls_key_file for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_loglevel (default: $smtpd_tls_loglevel)
       Enable additional Postfix tlsproxy(8) server logging of TLS activity.  Each logging  level
       also   includes	 the   information   that  is  logged  at  a  lower  logging  level.  See
       smtpd_tls_loglevel for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_mandatory_ciphers (default: $smtpd_tls_mandatory_ciphers)
       The minimum TLS cipher grade that the Postfix tlsproxy(8) server will use  with	mandatory
       TLS encryption. See smtpd_tls_mandatory_ciphers for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_mandatory_exclude_ciphers (default: $smtpd_tls_mandatory_exclude_ciphers)
       Additional  list  of ciphers or cipher types to exclude from the tlsproxy(8) server cipher
       list at mandatory TLS security levels.  See smtpd_tls_mandatory_exclude_ciphers	for  fur-
       ther details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_mandatory_protocols (default: $smtpd_tls_mandatory_protocols)
       The  SSL/TLS  protocols	accepted  by  the  Postfix  tlsproxy(8) server with mandatory TLS
       encryption. If the list is empty, the server supports all available SSL/TLS protocol  ver-
       sions.  See smtpd_tls_mandatory_protocols for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_protocols (default: $smtpd_tls_protocols)
       List  of  TLS  protocols  that the Postfix tlsproxy(8) server will exclude or include with
       opportunistic TLS encryption. See smtpd_tls_protocols for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_req_ccert (default: $smtpd_tls_req_ccert)
       With mandatory TLS encryption, require a trusted remote SMTP client certificate	in  order
       to allow TLS connections to proceed.  See smtpd_tls_req_ccert for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_security_level (default: $smtpd_tls_security_level)
       The  SMTP TLS security level for the Postfix tlsproxy(8) server; when a non-empty value is
       specified, this overrides the obsolete parameters smtpd_use_tls and smtpd_enforce_tls. See
       smtpd_tls_security_level for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_tls_session_cache_timeout (default: $smtpd_tls_session_cache_timeout)
       The  expiration	time of Postfix tlsproxy(8) server TLS session cache information. A cache
       cleanup is performed  periodically  every  $smtpd_tls_session_cache_timeout  seconds.  See
       smtpd_tls_session_cache_timeout for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_use_tls (default: $smtpd_use_tls)
       Opportunistic  TLS:  announce  STARTTLS	support  to SMTP clients, but do not require that
       clients use TLS encryption. See smtpd_use_tls for further details.

       This feature is available in Postfix 2.8 and later.

tlsproxy_watchdog_timeout (default: 10s)
       How much time a tlsproxy(8) process may take to process local or remote I/O before  it  is
       terminated  by  a  built-in  watchdog  timer.   This  is  a safety mechanism that prevents
       tlsproxy(8) from becoming non-responsive due to a bug in Postfix itself or in system soft-
       ware.   To  avoid  false  alarms and unnecessary cache corruption this limit cannot be set
       under 10s.

       Specify a non-zero time value (an integral value plus an optional one-letter  suffix  that
       specifies  the  time  unit).  Time units: s (seconds), m (minutes), h (hours), d (days), w
       (weeks).

       This feature is available in Postfix 2.8.

trace_service_name (default: trace)
       The name of the trace service. This service is implemented by  the  bounce(8)  daemon  and
       maintains  a  record  of  mail deliveries and produces a mail delivery report when verbose
       delivery is requested with "sendmail -v".

       This feature is available in Postfix 2.1 and later.

transport_delivery_slot_cost (default: $default_delivery_slot_cost)
       A transport-specific override for the default_delivery_slot_cost  parameter  value,  where
       transport is the master.cf name of the message delivery transport.

transport_delivery_slot_discount (default: $default_delivery_slot_discount)
       A  transport-specific  override	for  the  default_delivery_slot_discount parameter value,
       where transport is the master.cf name of the message delivery transport.

transport_delivery_slot_loan (default: $default_delivery_slot_loan)
       A transport-specific override for the default_delivery_slot_loan  parameter  value,  where
       transport is the master.cf name of the message delivery transport.

transport_destination_concurrency_failed_cohort_limit	 (default:   $default_destination_concur-
       rency_failed_cohort_limit)
       A transport-specific override for the  default_destination_concurrency_failed_cohort_limit
       parameter value, where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5 and later.

transport_destination_concurrency_limit (default: $default_destination_concurrency_limit)
       A  transport-specific  override	for  the  default_destination_concurrency_limit parameter
       value, where transport is the master.cf name of the message delivery transport.

transport_destination_concurrency_negative_feedback    (default:     $default_destination_concur-
       rency_negative_feedback)
       A  transport-specific  override	for the default_destination_concurrency_negative_feedback
       parameter value, where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5 and later.

transport_destination_concurrency_positive_feedback    (default:     $default_destination_concur-
       rency_positive_feedback)
       A  transport-specific  override	for the default_destination_concurrency_positive_feedback
       parameter value, where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5 and later.

transport_destination_rate_delay (default: $default_destination_rate_delay)
       A transport-specific override  for  the	default_destination_rate_delay	parameter  value,
       where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5 and later.

transport_destination_recipient_limit (default: $default_destination_recipient_limit)
       A transport-specific override for the default_destination_recipient_limit parameter value,
       where transport is the master.cf name of the message delivery transport.

transport_extra_recipient_limit (default: $default_extra_recipient_limit)
       A transport-specific override for the default_extra_recipient_limit parameter value, where
       transport is the master.cf name of the message delivery transport.

transport_initial_destination_concurrency (default: $initial_destination_concurrency)
       A  transport-specific  override	for  the initial_destination_concurrency parameter value,
       where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.5 and later.

transport_maps (default: empty)
       Optional lookup tables with mappings from recipient address to  (message  delivery  trans-
       port, next-hop destination).  See transport(5) for details.

       Specify	zero  or  more	"type:table"  lookup  tables.  If you use this feature with local
       files, run "postmap /etc/postfix/transport" after making a change.

       For safety reasons, as of Postfix 2.3 this feature does not allow $number substitutions in
       regular expression maps.

       Examples:

       transport_maps = dbm:/etc/postfix/transport
       transport_maps = hash:/etc/postfix/transport

transport_minimum_delivery_slots (default: $default_minimum_delivery_slots)
       A  transport-specific  override	for  the  default_minimum_delivery_slots parameter value,
       where transport is the master.cf name of the message delivery transport.

transport_recipient_limit (default: $default_recipient_limit)
       A transport-specific override  for  the	default_recipient_limit  parameter  value,  where
       transport is the master.cf name of the message delivery transport.

transport_recipient_refill_delay (default: $default_recipient_refill_delay)
       A  transport-specific  override	for  the  default_recipient_refill_delay parameter value,
       where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.4 and later.

transport_recipient_refill_limit (default: $default_recipient_refill_limit)
       A transport-specific override  for  the	default_recipient_refill_limit	parameter  value,
       where transport is the master.cf name of the message delivery transport.

       This feature is available in Postfix 2.4 and later.

transport_retry_time (default: 60s)
       The time between attempts by the Postfix queue manager to contact a malfunctioning message
       delivery transport.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

transport_time_limit (default: $command_time_limit)
       A  transport-specific override for the command_time_limit parameter value, where transport
       is the master.cf name of the message delivery transport.

trigger_timeout (default: 10s)
       The time limit for sending a trigger to a Postfix daemon (for example,  the  pickup(8)  or
       qmgr(8) daemon). This time limit prevents programs from getting stuck when the mail system
       is under heavy load.

       Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).   The  default  time
       unit is s (seconds).

undisclosed_recipients_header (default: see postconf -d output)
       Message	header	that the Postfix cleanup(8) server inserts when a message contains no To:
       or Cc: message header. With Postfix 2.8 and later, the default value is empty. With  Post-
       fix 2.4-2.7, specify an empty value to disable this feature.

       Example:

       # Default value before Postfix 2.8.
       # Note: the ":" and ";" are both required.
       undisclosed_recipients_header = To: undisclosed-recipients:;

unknown_address_reject_code (default: 450)
       The  numerical  Postfix	SMTP  server  response code when a sender or recipient address is
       rejected by the reject_unknown_sender_domain or	reject_unknown_recipient_domain  restric-
       tion.  The response is always 450 in case of a temporary DNS error.

       Do not change this unless you have a complete understanding of RFC 2821.

unknown_address_tempfail_action (default: $reject_tempfail_action)
       The    Postfix	 SMTP	 server's    action    when    reject_unknown_sender_domain    or
       reject_unknown_recipient_domain fail due to a temporary error condition.  Specify  "defer"
       to  defer  the  remote SMTP client request immediately. With the default "defer_if_permit"
       action, the Postfix SMTP server continues to look for opportunities to  reject  mail,  and
       defers the client request only if it would otherwise be accepted.

       This feature is available in Postfix 2.6 and later.

unknown_client_reject_code (default: 450)
       The  numerical  Postfix	SMTP server response code when a client without valid address <=>
       name mapping is rejected  by  the  reject_unknown_client_hostname  restriction.	The  SMTP
       server always replies with 450 when the mapping failed due to a temporary error condition.

       Do not change this unless you have a complete understanding of RFC 2821.

unknown_helo_hostname_tempfail_action (default: $reject_tempfail_action)
       The  Postfix SMTP server's action when reject_unknown_helo_hostname fails due to an tempo-
       rary error condition. Specify "defer" to defer the remote SMTP client request immediately.
       With  the  default "defer_if_permit" action, the Postfix SMTP server continues to look for
       opportunities to reject mail, and defers the client request only if it would otherwise  be
       accepted.

       This feature is available in Postfix 2.6 and later.

unknown_hostname_reject_code (default: 450)
       The  numerical Postfix SMTP server response code when the hostname specified with the HELO
       or EHLO command is rejected by the reject_unknown_helo_hostname restriction.

       Do not change this unless you have a complete understanding of RFC 2821.

unknown_local_recipient_reject_code (default: 550)
       The numerical Postfix SMTP server response code when a recipient  address  is  local,  and
       $local_recipient_maps specifies a list of lookup tables that does not match the recipient.
       A recipient address is local when its domain matches $mydestination, $proxy_interfaces  or
       $inet_interfaces.

       The  default  setting is 550 (reject mail) but it is safer to initially use 450 (try again
       later) so you have time to find out if your local_recipient_maps settings are OK.

       Example:

       unknown_local_recipient_reject_code = 450

       This feature is available in Postfix 2.0 and later.

unknown_relay_recipient_reject_code (default: 550)
       The  numerical  Postfix	SMTP  server  reply  code  when  a  recipient	address   matches
       $relay_domains,	and  relay_recipient_maps specifies a list of lookup tables that does not
       match the recipient address.

       This feature is available in Postfix 2.0 and later.

unknown_virtual_alias_reject_code (default: 550)
       The SMTP server reply code when a recipient address  matches  $virtual_alias_domains,  and
       $virtual_alias_maps  specifies  a  list of lookup tables that does not match the recipient
       address.

       This feature is available in Postfix 2.0 and later.

unknown_virtual_mailbox_reject_code (default: 550)
       The SMTP server reply code when a recipient address matches $virtual_mailbox_domains,  and
       $virtual_mailbox_maps  specifies a list of lookup tables that does not match the recipient
       address.

       This feature is available in Postfix 2.0 and later.

unverified_recipient_defer_code (default: 450)
       The numerical Postfix SMTP server response when a recipient address probe fails due  to	a
       temporary error condition.

       Unlike elsewhere in Postfix, you can specify 250 in order to accept the address anyway.

       Do not change this unless you have a complete understanding of RFC 2821.

       This feature is available in Postfix 2.6 and later.

unverified_recipient_reject_code (default: 450)
       The  numerical  Postfix	SMTP  server response when a recipient address is rejected by the
       reject_unverified_recipient restriction.

       Unlike elsewhere in Postfix, you can specify 250 in order to accept the address anyway.

       Do not change this unless you have a complete understanding of RFC 2821.

       This feature is available in Postfix 2.1 and later.

unverified_recipient_reject_reason (default: empty)
       The Postfix SMTP server's reply when rejecting mail with  reject_unverified_recipient.  Do
       not  include  the  numeric  SMTP  reply	code or the enhanced status code. By default, the
       response includes actual address verification details.

       Example:

       unverified_recipient_reject_reason = Recipient address lookup failed

       This feature is available in Postfix 2.6 and later.

unverified_recipient_tempfail_action (default: $reject_tempfail_action)
       The Postfix SMTP server's action when reject_unverified_recipient fails due to a temporary
       error condition. Specify "defer" to defer the remote SMTP client request immediately. With
       the default "defer_if_permit" action, the Postfix SMTP server continues to look for oppor-
       tunities  to  reject  mail,  and  defers  the client request only if it would otherwise be
       accepted.

       This feature is available in Postfix 2.6 and later.

unverified_sender_defer_code (default: 450)
       The numerical Postfix SMTP server response code when a sender address probe fails due to a
       temporary error condition.

       Unlike elsewhere in Postfix, you can specify 250 in order to accept the address anyway.

       Do not change this unless you have a complete understanding of RFC 2821.

       This feature is available in Postfix 2.6 and later.

unverified_sender_reject_code (default: 450)
       The  numerical  Postfix	SMTP server response code when a recipient address is rejected by
       the reject_unverified_sender restriction.

       Unlike elsewhere in Postfix, you can specify 250 in order to accept the address anyway.

       Do not change this unless you have a complete understanding of RFC 2821.

       This feature is available in Postfix 2.1 and later.

unverified_sender_reject_reason (default: empty)
       The Postfix SMTP server's reply when rejecting mail with reject_unverified_sender. Do  not
       include	the numeric SMTP reply code or the enhanced status code. By default, the response
       includes actual address verification details.

       Example:

       unverified_sender_reject_reason = Sender address lookup failed

       This feature is available in Postfix 2.6 and later.

unverified_sender_tempfail_action (default: $reject_tempfail_action)
       The Postfix SMTP server's action when reject_unverified_sender fails due  to  a	temporary
       error condition. Specify "defer" to defer the remote SMTP client request immediately. With
       the default "defer_if_permit" action, the Postfix SMTP server continues to look for oppor-
       tunities  to  reject  mail,  and  defers  the client request only if it would otherwise be
       accepted.

       This feature is available in Postfix 2.6 and later.

verp_delimiter_filter (default: -=+)
       The characters Postfix accepts as VERP delimiter characters  on	the  Postfix  sendmail(1)
       command line and in SMTP commands.

       This feature is available in Postfix 1.1 and later.

virtual_alias_domains (default: $virtual_alias_maps)
       Postfix	is  final  destination	for the specified list of virtual alias domains, that is,
       domains for which all addresses are aliased to addresses in other local or remote domains.
       The  SMTP  server  validates recipient addresses with $virtual_alias_maps and rejects non-
       existent recipients. See also the virtual alias domain class in	the  ADDRESS_CLASS_README
       file

       This feature is available in Postfix 2.0 and later. The default value is backwards compat-
       ible with Postfix version 1.1.

       The default value is $virtual_alias_maps so that you can keep all information  about  vir-
       tual  alias domains in one place.  If you have many users, it is better to separate infor-
       mation that changes more frequently (virtual address -> local or remote	address  mapping)
       from information that changes less frequently (the list of virtual domain names).

       Specify	a  list of host or domain names, "/file/name" or "type:table" patterns, separated
       by commas and/or whitespace. A  "/file/name"  pattern  is  replaced  by	its  contents;	a
       "type:table"  lookup  table  is	matched  when  a table entry matches a lookup string (the
       lookup result is ignored).  Continue long lines by starting the next line with whitespace.
       Specify	"!pattern" to exclude a host or domain name from the list. The form "!/file/name"
       is supported only in Postfix version 2.4 and later.

       See also the VIRTUAL_README and ADDRESS_CLASS_README documents for further information.

       Example:

       virtual_alias_domains = virtual1.tld virtual2.tld

virtual_alias_expansion_limit (default: 1000)
       The maximal number of addresses that virtual alias expansion produces from  each  original
       recipient.

       This feature is available in Postfix 2.1 and later.

virtual_alias_maps (default: $virtual_maps)
       Optional  lookup  tables  that  alias specific mail addresses or domains to other local or
       remote address.	The table format and lookups are documented in virtual(5). For	an  over-
       view of Postfix address manipulations see the ADDRESS_REWRITING_README document.

       This feature is available in Postfix 2.0 and later. The default value is backwards compat-
       ible with Postfix version 1.1.

       If you use this feature with  indexed  files,  run  "postmap  /etc/postfix/virtual"  after
       changing the file.

       Examples:

       virtual_alias_maps = dbm:/etc/postfix/virtual
       virtual_alias_maps = hash:/etc/postfix/virtual

virtual_alias_recursion_limit (default: 1000)
       The  maximal  nesting  depth of virtual alias expansion.  Currently the recursion limit is
       applied only to the left branch of the expansion graph, so the depth of the  tree  can  in
       the  worst  case  reach the sum of the expansion and recursion limits.  This may change in
       the future.

       This feature is available in Postfix 2.1 and later.

virtual_destination_concurrency_limit (default: $default_destination_concurrency_limit)
       The maximal number of parallel deliveries to the same destination via the virtual  message
       delivery  transport.  This  limit  is  enforced by the queue manager. The message delivery
       transport name is the first field in the entry in the master.cf file.

virtual_destination_recipient_limit (default: $default_destination_recipient_limit)
       The maximal number of recipients per message for the virtual message  delivery  transport.
       This  limit  is	enforced by the queue manager. The message delivery transport name is the
       first field in the entry in the master.cf file.

       Setting this parameter to a value of 1 changes the meaning of  virtual_destination_concur-
       rency_limit from concurrency per domain into concurrency per recipient.

virtual_gid_maps (default: empty)
       Lookup tables with the per-recipient group ID for virtual(8) mailbox delivery.

       In  a  lookup  table,  specify  a left-hand side of "@domain.tld" to match any user in the
       specified domain that does not have a specific "user@domain.tld" entry.

       When a recipient address has an optional address extension (user+foo@domain.tld), the vir-
       tual(8)	delivery  agent  looks	up  the full address first, and when the lookup fails, it
       looks up the unextended address (user@domain.tld).

       Note 1: for security reasons, the virtual(8) delivery agent disallows  regular  expression
       substitution  of  $1  etc.  in regular expression lookup tables, because that would open a
       security hole.

       Note 2: for security reasons, the virtual(8) delivery agent will silently ignore  requests
       to  use	the  proxymap(8)  server. Instead it will open the table directly. Before Postfix
       version 2.2, the virtual(8) delivery agent will terminate with a fatal error.

virtual_mailbox_base (default: empty)
       A prefix that the virtual(8) delivery agent prepends to all pathname  results  from  $vir-
       tual_mailbox_maps  table  lookups.  This is a safety measure to ensure that an out of con-
       trol map doesn't litter the file system with mailboxes.	While virtual_mailbox_base  could
       be set to "/", this setting isn't recommended.

       Example:

       virtual_mailbox_base = /var/mail

virtual_mailbox_domains (default: $virtual_mailbox_maps)
       Postfix	is final destination for the specified list of domains; mail is delivered via the
       $virtual_transport mail delivery transport.  By default this  is  the  Postfix  virtual(8)
       delivery  agent.  The SMTP server validates recipient addresses with $virtual_mailbox_maps
       and rejects mail for non-existent recipients.  See also the virtual mailbox  domain  class
       in the ADDRESS_CLASS_README file.

       This parameter expects the same syntax as the mydestination configuration parameter.

       This feature is available in Postfix 2.0 and later. The default value is backwards compat-
       ible with Postfix version 1.1.

virtual_mailbox_limit (default: 51200000)
       The maximal size in bytes of an individual virtual(8) mailbox or maildir file, or zero (no
       limit).

virtual_mailbox_lock (default: see postconf -d output)
       How  to	lock  a  UNIX-style virtual(8) mailbox before attempting delivery.  For a list of
       available file locking methods, use the "postconf -l" command.

       This setting is ignored with maildir style delivery,  because  such  deliveries	are  safe
       without application-level locks.

       Note  1: the dotlock method requires that the recipient UID or GID has write access to the
       parent directory of the recipient's mailbox file.

       Note 2: the default setting of this parameter is system dependent.

virtual_mailbox_maps (default: empty)
       Optional lookup tables with all valid addresses in the domains that  match  $virtual_mail-
       box_domains.

       In  a  lookup  table,  specify  a left-hand side of "@domain.tld" to match any user in the
       specified domain that does not have a specific "user@domain.tld" entry.

       The virtual(8) delivery agent uses this table to look  up  the  per-recipient  mailbox  or
       maildir	pathname.   If the lookup result ends in a slash ("/"), maildir-style delivery is
       carried out, otherwise the path is assumed to specify a	UNIX-style  mailbox  file.   Note
       that $virtual_mailbox_base is unconditionally prepended to this path.

       When a recipient address has an optional address extension (user+foo@domain.tld), the vir-
       tual(8) delivery agent looks up the full address first, and  when  the  lookup  fails,  it
       looks up the unextended address (user@domain.tld).

       Note  1:  for security reasons, the virtual(8) delivery agent disallows regular expression
       substitution of $1 etc. in regular expression lookup tables, because  that  would  open	a
       security hole.

       Note  2: for security reasons, the virtual(8) delivery agent will silently ignore requests
       to use the proxymap(8) server. Instead it will open the	table  directly.  Before  Postfix
       version 2.2, the virtual(8) delivery agent will terminate with a fatal error.

virtual_maps (default: empty)
       Optional  lookup  tables  with  a) names of domains for which all addresses are aliased to
       addresses in other local or remote domains, and b) addresses that are aliased to addresses
       in other local or remote domains.  Available before Postfix version 2.0. With Postfix ver-
       sion 2.0 and later, this is replaced by separate controls: virtual_alias_domains and  vir-
       tual_alias_maps.

virtual_minimum_uid (default: 100)
       The  minimum  user  ID  value  that the virtual(8) delivery agent accepts as a result from
       $virtual_uid_maps table lookup.	Returned values less than this will be rejected, and  the
       message will be deferred.

virtual_transport (default: virtual)
       The default mail delivery transport and next-hop destination for final delivery to domains
       listed with $virtual_mailbox_domains.  This information can be overruled with  the  trans-
       port(5) table.

       Specify	a  string  of  the  form transport:nexthop, where transport is the name of a mail
       delivery transport defined in master.cf.  The :nexthop destination is optional; its syntax
       is documented in the manual page of the corresponding delivery agent.

       This feature is available in Postfix 2.0 and later.

virtual_uid_maps (default: empty)
       Lookup tables with the per-recipient user ID that the virtual(8) delivery agent uses while
       writing to the recipient's mailbox.

       In a lookup table, specify a left-hand side of "@domain.tld" to	match  any  user  in  the
       specified domain that does not have a specific "user@domain.tld" entry.

       When a recipient address has an optional address extension (user+foo@domain.tld), the vir-
       tual(8) delivery agent looks up the full address first, and  when  the  lookup  fails,  it
       looks up the unextended address (user@domain.tld).

       Note  1:  for security reasons, the virtual(8) delivery agent disallows regular expression
       substitution of $1 etc. in regular expression lookup tables, because  that  would  open	a
       security hole.

       Note  2: for security reasons, the virtual(8) delivery agent will silently ignore requests
       to use the proxymap(8) server. Instead it will open the	table  directly.  Before  Postfix
       version 2.2, the virtual(8) delivery agent will terminate with a fatal error.

SEE ALSO
       postconf(1), Postfix configuration parameter maintenance
       master(5), Postfix daemon configuration maintenance

LICENSE
       The Secure Mailer license must be distributed with this software.

AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

										      POSTCONF(5)


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