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RedHat 9 (Linux i386) - man page for virtual (redhat section 8)

VIRTUAL(8)			     System Manager's Manual			       VIRTUAL(8)

NAME
       virtual - Postfix virtual domain mail delivery agent

SYNOPSIS
       virtual [generic Postfix daemon options]

DESCRIPTION
       The virtual delivery agent is designed for virtual mail hosting services. Originally based
       on the Postfix local delivery agent, this agent looks up recipients with  map  lookups  of
       their  full  recipient  address, instead of using hard-coded unix password file lookups of
       the address local part only.

       This delivery agent only delivers mail.	Other features such as mail  forwarding,  out-of-
       office  notifications,  etc.,  must  be	configured via virtual maps or via similar lookup
       mechanisms.

MAILBOX LOCATION
       The mailbox location is controlled by the  virtual_mailbox_base	and  virtual_mailbox_maps
       configuration  parameters  (see	below).  The virtual_mailbox_maps table is indexed by the
       full recipient address.

       The mailbox pathname is constructed as follows:

	 $virtual_mailbox_base/$virtual_mailbox_maps(recipient)

       where recipient is the full recipient address.

UNIX MAILBOX FORMAT
       When the mailbox location does not end in /, the message is delivered in UNIX mailbox for-
       mat.   This format stores multiple messages in one textfile.

       The  virtual  delivery  agent  prepends a "From sender time_stamp" envelope header to each
       message, prepends a Delivered-To: message header  with  the  envelope  recipient  address,
       prepends  a  Return-Path:  message  header  with the envelope sender address, prepends a >
       character to lines beginning with "From ", and appends an empty line.

       The mailbox is locked for exclusive access while delivery is in progress. In case of prob-
       lems, an attempt is made to truncate the mailbox to its original length.

QMAIL MAILDIR FORMAT
       When  the  mailbox  location  ends in /, the message is delivered in qmail maildir format.
       This format stores one message per file.

       The virtual delivery agent daemon prepends a Delivered-To: message header with  the  enve-
       lope recipient address and prepends a Return-Path: message header with the envelope sender
       address.

       By definition, maildir format does not  require	file  locking  during  mail  delivery  or
       retrieval.

MAILBOX OWNERSHIP
       Mailbox	ownership  is  controlled  by  the  virtual_uid_maps  and virtual_gid_maps lookup
       tables, which are indexed with the full recipient address. Each table  provides	a  string
       with the numerical user and group ID, respectively.

       The  virtual_minimum_uid  parameter imposes a lower bound on numerical user ID values that
       may be specified in any virtual_owner_maps or virtual_uid_maps.

SECURITY
       The virtual delivery agent is not security sensitive, provided that the lookup tables with
       recipient user/group ID information are adequately protected. This program is not designed
       to run chrooted.

STANDARDS
       RFC 822 (ARPA Internet Text Messages)

DIAGNOSTICS
       Mail bounces when the recipient has no mailbox or when the recipient is over  disk  quota.
       In all other cases, mail for an existing recipient is deferred and a warning is logged.

       Problems and transactions are logged to syslogd(8).  Corrupted message files are marked so
       that the queue manager can move them to the corrupt queue afterwards.

       Depending on the setting of the notify_classes parameter, the postmaster  is  notified  of
       bounces and of other trouble.

BUGS
       This delivery agent silently ignores address extensions.

       Postfix	should have lookup tables that can return multiple result attributes. In order to
       avoid the inconvenience of maintaining three tables, use an LDAP or MYSQL database.

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

Mailbox delivery
       virtual_mailbox_base
	      Specifies a path that is prepended to all mailbox or  maildir  paths.   This  is	a
	      safety measure to ensure that an out of control map in virtual_mailbox_maps doesn't
	      litter the filesystem with mailboxes.  While it could be set to "/",  this  setting
	      isn't recommended.

       virtual_mailbox_maps (regexp maps disallowed)
	      Recipients  are  looked  up in these maps to determine the path to their mailbox or
	      maildir. If the returned path ends in a slash ("/"), maildir-style delivery is car-
	      ried out, otherwise the path is assumed to specify a UNIX-style mailbox file.

	      Note that virtual_mailbox_base is unconditionally prepended to this path.

       virtual_minimum_uid
	      Specifies a minimum uid that will be accepted as a return from a virtual_owner_maps
	      or virtual_uid_maps lookup.  Returned values less than this will be  rejected,  and
	      the message will be deferred.

       virtual_uid_maps (regexp maps disallowed)
	      Recipients  are  looked  up  in these maps to determine the user ID to be used when
	      writing to the target mailbox.

       virtual_gid_maps (regexp maps disallowed)
	      Recipients are looked up in these maps to determine the group ID to  be  used  when
	      writing to the target mailbox.

Locking controls
       virtual_mailbox_lock
	      How  to lock UNIX-style mailboxes: one or more of flock, fcntl or dotlock. The dot-
	      lock method requires that the recipient UID or GID has write access to  the  parent
	      directory of the mailbox file.

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

	      Use the command postconf -l to find out what locking methods are available on  your
	      system.

       deliver_lock_attempts
	      Limit  the  number of attempts to acquire an exclusive lock on a UNIX-style mailbox
	      file.

       deliver_lock_delay
	      Time (default: seconds) between successive attempts to acquire an exclusive lock on
	      a UNIX-style mailbox file. The actual delay is slightly randomized.

       stale_lock_time
	      Limit  the  time	after which a stale lockfile is removed (applicable to UNIX-style
	      mailboxes only).

Resource controls
       virtual_destination_concurrency_limit
	      Limit the number of parallel deliveries to the same domain via the virtual delivery
	      agent.   The  default limit is taken from the default_destination_concurrency_limit
	      parameter.  The limit is enforced by the Postfix queue manager.

       virtual_destination_recipient_limit
	      Limit the number of recipients per message delivery via the virtual delivery agent.
	      The  default limit is taken from the default_destination_recipient_limit parameter.
	      The limit is enforced by the Postfix queue manager.

       virtual_mailbox_limit
	      The maximal size in bytes of a mailbox or maildir file.  Set to zero to disable the
	      limit.

HISTORY
       This  agent was originally based on the Postfix local delivery agent. Modifications mainly
       consisted of removing code that either was not applicable or that was  not  safe  in  this
       context: aliases, ~user/.forward files, delivery to "|command" or to /file/name.

       The Delivered-To: header appears in the qmail system by Daniel Bernstein.

       The maildir structure appears in the qmail system by Daniel Bernstein.

SEE ALSO
       bounce(8) non-delivery status reports
       syslogd(8) system logging
       qmgr(8) queue manager

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

       Andrew McNamara
       andrewm@connect.com.au
       connect.com.au Pty. Ltd.
       Level 3, 213 Miller St
       North Sydney 2060, NSW, Australia

										       VIRTUAL(8)


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