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

VIRTUAL(5)			       File Formats Manual			       VIRTUAL(5)

NAME
       virtual - Postfix virtual alias table format

SYNOPSIS
       postmap /etc/postfix/virtual

       postmap -q "string" /etc/postfix/virtual

       postmap -q - /etc/postfix/virtual <inputfile

DESCRIPTION
       The  optional  virtual(5) alias table rewrites recipient addresses for all local, all vir-
       tual, and all remote mail destinations.	This is unlike the aliases(5) table which is used
       only  for  local(8)  delivery.	Virtual  aliasing is recursive, and is implemented by the
       Postfix cleanup(8) daemon before mail is queued.

       The main applications of virtual aliasing are:

       o      To redirect mail for one address to one or more addresses.

       o      To implement virtual alias domains where all addresses are aliased to addresses  in
	      other domains.

	      Virtual  alias domains are not to be confused with the virtual mailbox domains that
	      are implemented with the Postfix virtual(8) mail delivery agent. With virtual mail-
	      box domains, each recipient address can have its own mailbox.

       Virtual aliasing is applied only to recipient envelope addresses, and does not affect mes-
       sage headers.  Use canonical(5) mapping to rewrite header and envelope addresses  in  gen-
       eral.

       Normally,  the  virtual(5) alias table is specified as a text file that serves as input to
       the postmap(1) command.	The result, an indexed file in dbm or db format, is used for fast
       searching  by  the  mail  system.  Execute  the	command "postmap /etc/postfix/virtual" to
       rebuild an indexed file after changing the corresponding text file.

       When the table is provided via other means such as NIS, LDAP or SQL, the same lookups  are
       done as for ordinary indexed files.

       Alternatively,  the  table  can be provided as a regular-expression map where patterns are
       given as regular expressions, or lookups can be directed to  TCP-based  server.	In  those
       case,  the  lookups are done in a slightly different way as described below under "REGULAR
       EXPRESSION TABLES" or "TCP-BASED TABLES".

CASE FOLDING
       The search string is folded to lowercase before database lookup. As of  Postfix	2.3,  the
       search string is not case folded with database types such as regexp: or pcre: whose lookup
       fields can match both upper and lower case.

TABLE FORMAT
       The input format for the postmap(1) command is as follows:

       pattern result
	      When pattern matches a mail address, replace it by the corresponding result.

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

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

TABLE SEARCH ORDER
       With lookups from indexed files such as DB or DBM, or from networked tables such  as  NIS,
       LDAP or SQL, patterns are tried in the order as listed below:

       user@domain address, address, ...
	      Redirect mail for user@domain to address.  This form has the highest precedence.

       user address, address, ...
	      Redirect	mail  for user@site to address when site is equal to $myorigin, when site
	      is  listed  in  $mydestination,  or  when  it  is  listed  in  $inet_interfaces  or
	      $proxy_interfaces.

	      This  functionality  overlaps  with functionality of the local aliases(5) database.
	      The difference is that virtual(5) mapping can be applied to non-local addresses.

       @domain address, address, ...
	      Redirect mail for other users in domain to  address.   This  form  has  the  lowest
	      precedence.

	      Note:  @domain is a wild-card. With this form, the Postfix SMTP server accepts mail
	      for any recipient in domain, regardless of whether that recipient exists.  This may
	      turn  your  mail	system	into a backscatter source: Postfix first accepts mail for
	      non-existent recipients and then tries to return that mail  as  "undeliverable"  to
	      the often forged sender address.

RESULT ADDRESS REWRITING
       The lookup result is subject to address rewriting:

       o      When the result has the form @otherdomain, the result becomes the same user in oth-
	      erdomain.  This works only for the first address in a multi-address lookup result.

       o      When "append_at_myorigin=yes", append "@$myorigin" to addresses without "@domain".

       o      When "append_dot_mydomain=yes", append ".$mydomain" to addresses without ".domain".

ADDRESS EXTENSION
       When  a	mail  address  localpart  contains  the  optional  recipient   delimiter   (e.g.,
       user+foo@domain),  the lookup order becomes: user+foo@domain, user@domain, user+foo, user,
       and @domain.

       The propagate_unmatched_extensions parameter controls whether an unmatched address  exten-
       sion (+foo) is propagated to the result of table lookup.

VIRTUAL ALIAS DOMAINS
       Besides	virtual  aliases,  the	virtual alias table can also be used to implement virtual
       alias domains. With a virtual  alias  domain,  all  recipient  addresses  are  aliased  to
       addresses in other domains.

       Virtual	alias  domains	are  not to be confused with the virtual mailbox domains that are
       implemented with the Postfix virtual(8) mail delivery agent. With virtual mailbox domains,
       each recipient address can have its own mailbox.

       With  a	virtual alias domain, the virtual domain has its own user name space. Local (i.e.
       non-virtual) usernames are not visible in a virtual alias  domain.  In  particular,  local
       aliases(5) and local mailing lists are not visible as localname@virtual-alias.domain.

       Support for a virtual alias domain looks like:

       /etc/postfix/main.cf:
	   virtual_alias_maps = hash:/etc/postfix/virtual

       Note:  some  systems use dbm databases instead of hash.	See the output from "postconf -m"
       for available database types.

       /etc/postfix/virtual:
	   virtual-alias.domain     anything (right-hand content does not matter)
	   postmaster@virtual-alias.domain  postmaster
	   user1@virtual-alias.domain	    address1
	   user2@virtual-alias.domain	    address2, address3

       The virtual-alias.domain anything entry is required for a virtual  alias  domain.  Without
       this  entry, mail is rejected with "relay access denied", or bounces with "mail loops back
       to myself".

       Do not specify virtual alias domain names in the main.cf  mydestination	or  relay_domains
       configuration parameters.

       With  a virtual alias domain, the Postfix SMTP server accepts mail for known-user@virtual-
       alias.domain, and rejects mail for unknown-user@virtual-alias.domain as undeliverable.

       Instead of specifying the virtual alias domain name via the virtual_alias_maps table,  you
       may  also  specify it via the main.cf virtual_alias_domains configuration parameter.  This
       latter parameter uses the same syntax as the main.cf mydestination  configuration  parame-
       ter.

REGULAR EXPRESSION TABLES
       This section describes how the table lookups change when the table is given in the form of
       regular expressions. For a description of regular expression lookup table syntax, see reg-
       exp_table(5) or pcre_table(5).

       Each  pattern  is  a regular expression that is applied to the entire address being looked
       up. Thus, user@domain mail addresses are not broken up into their user  and  @domain  con-
       stituent parts, nor is user+foo broken up into user and foo.

       Patterns are applied in the order as specified in the table, until a pattern is found that
       matches the search string.

       Results are the same as with indexed file lookups, with the additional feature that paren-
       thesized substrings from the pattern can be interpolated as $1, $2 and so on.

TCP-BASED TABLES
       This  section  describes  how the table lookups change when lookups are directed to a TCP-
       based server. For a description of the TCP  client/server  lookup  protocol,  see  tcp_ta-
       ble(5).	This feature is not available up to and including Postfix version 2.4.

       Each  lookup operation uses the entire address once.  Thus, user@domain mail addresses are
       not broken up into their user and @domain constituent parts, nor  is  user+foo  broken  up
       into user and foo.

       Results are the same as with indexed file lookups.

BUGS
       The table format does not understand quoting conventions.

CONFIGURATION PARAMETERS
       The  following  main.cf	parameters are especially relevant to this topic. See the Postfix
       main.cf file for syntax details and for default values. Use the "postfix  reload"  command
       after a configuration change.

       virtual_alias_maps
	      List of virtual aliasing tables.

       virtual_alias_domains
	      List  of	virtual  alias	domains.  This	uses the same syntax as the mydestination
	      parameter.

       propagate_unmatched_extensions
	      A list of address rewriting or forwarding  mechanisms  that  propagate  an  address
	      extension from the original address to the result.  Specify zero or more of canoni-
	      cal, virtual, alias, forward, include, or generic.

       Other parameters of interest:

       inet_interfaces
	      The network interface addresses that this system receives mail  on.   You  need  to
	      stop and start Postfix when this parameter changes.

       mydestination
	      List of domains that this mail system considers local.

       myorigin
	      The domain that is appended to any address that does not have a domain.

       owner_request_special
	      Give special treatment to owner-xxx and xxx-request addresses.

       proxy_interfaces
	      Other interfaces that this machine receives mail on by way of a proxy agent or net-
	      work address translator.

SEE ALSO
       cleanup(8), canonicalize and enqueue mail
       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters
       canonical(5), canonical address mapping

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       ADDRESS_REWRITING_README, address rewriting guide
       DATABASE_README, Postfix lookup table overview
       VIRTUAL_README, domain hosting guide

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

										       VIRTUAL(5)


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