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

       virtual - Postfix virtual domain mail delivery agent

       virtual [generic Postfix daemon options]

       The virtual(8) delivery agent is designed for virtual mail hosting ser-
       vices. Originally based on the Postfix local(8)  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_alias maps or via similar lookup mechanisms.

       The mailbox location is controlled by the virtual_mailbox_base and vir-
       tual_mailbox_maps  configuration  parameters  (see  below).   The  vir-
       tual_mailbox_maps   table  is  indexed  by  the  recipient  address  as
       described under TABLE SEARCH ORDER below.

       The mailbox pathname is constructed as follows:


       where recipient is the full recipient address.

       When the mailbox location does not end in /, the message  is  delivered
       in  UNIX  mailbox format.   This format stores multiple messages in one

       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 an X-Original-To: header  with
       the recipient address as given to Postfix, prepends a Return-Path: mes-
       sage 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 problems, an attempt is made to truncate the mail-
       box to its original length.

       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 final envelope recipient address, prepends an X-Origi-
       nal-To: header with the recipient address  as  given  to  Postfix,  and
       prepends  a  Return-Path:  message  header  with  the  envelope  sender

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

       Mailbox  ownership  is  controlled  by  the  virtual_uid_maps  and vir-
       tual_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_uid_maps.

       Normally,  a  lookup  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.

       The  search  order  is as follows. The search stops upon the first suc-
       cessful lookup.

       o      When  the  recipient  has  an  optional  address  extension  the
              user+extension@domain.tld address is looked up first.

              With Postfix versions before 2.1, the optional address extension
              is always ignored.

       o      The  user@domain.tld  address,  without  address  extension,  is
              looked up next.

       o      Finally, the recipient @domain is looked up.

       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, a table can be  provided  as  a  regular-expression  map
       where patterns are given as regular expressions. In that case, only the
       full recipient address is given to the regular-expression map.

       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.

       RFC 822 (ARPA Internet Text Messages)

       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  postmas-
       ter is notified of bounces and of other trouble.

       This  delivery agent supports address extensions in email addresses and
       in lookup table keys, but does not propagate address extension informa-
       tion to the result of table lookup.

       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.

       Changes to main.cf are picked up automatically, as virtual(8) processes
       run for only a limited amount of time. Use the command "postfix reload"
       to speed up a change.

       The  text  below provides only a parameter summary. See postconf(5) for
       more details including examples.

       virtual_mailbox_base (empty)
              A prefix that the virtual(8)  delivery  agent  prepends  to  all
              pathname results from $virtual_mailbox_maps table lookups.

       virtual_mailbox_maps (empty)
              Optional  lookup  tables with all valid addresses in the domains
              that match $virtual_mailbox_domains.

       virtual_minimum_uid (100)
              The minimum user ID value that  the  virtual(8)  delivery  agent
              accepts as a result from $virtual_uid_maps table lookup.

       virtual_uid_maps (empty)
              Lookup tables with the per-recipient user ID that the virtual(8)
              delivery agent uses while writing to the recipient's mailbox.

       virtual_gid_maps (empty)
              Lookup tables with the per-recipient  group  ID  for  virtual(8)
              mailbox delivery.

       Available in Postfix version 2.0 and later:

       virtual_mailbox_domains ($virtual_mailbox_maps)
              The  list  of domains that are delivered via the $virtual_trans-
              port mail delivery transport.

       virtual_transport (virtual)
              The default mail delivery transport for domains that  match  the
              $virtual_mailbox_domains parameter value.

       virtual_mailbox_lock (see 'postconf -d' output)
              How  to  lock  a UNIX-style virtual(8) mailbox before attempting

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

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

       stale_lock_time (500s)
              The time after which  a  stale  exclusive  mailbox  lockfile  is

       virtual_destination_concurrency_limit     ($default_destination_concur-
              The maximal number of parallel deliveries to the  same  destina-
              tion via the virtual message delivery transport.

       virtual_destination_recipient_limit       ($default_destination_recipi-
              The maximal number of recipients per delivery  via  the  virtual
              message delivery transport.

       virtual_mailbox_limit (51200000)
              The  maximal  size  in bytes of an individual mailbox or maildir
              file, or zero (no limit).

       config_directory (see 'postconf -d' output)
              The default location of the Postfix main.cf and  master.cf  con-
              figuration files.

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

       ipc_timeout (3600s)
              The time limit for sending  or  receiving  information  over  an
              internal communication channel.

       max_idle (100s)
              The  maximum  amount of time that an idle Postfix daemon process
              waits for the next service request before exiting.

       max_use (100)
              The maximal number of connection requests before a Postfix  dae-
              mon process terminates.

       process_id (read-only)
              The process ID of a Postfix command or daemon process.

       process_name (read-only)
              The process name of a Postfix command or daemon process.

       queue_directory (see 'postconf -d' output)
              The location of the Postfix top-level queue directory.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (postfix)
              The  mail  system  name that is prepended to the process name in
              syslog records, so that "smtpd"  becomes,  for  example,  "post-

       qmgr(8), queue manager
       bounce(8), delivery status reports
       postconf(5), configuration parameters
       syslogd(8), system logging

       Use "postconf readme_directory" or
       "postconf html_directory" to locate this information.
       VIRTUAL_README, domain hosting howto

       The Secure Mailer license must be distributed with this software.

       This  delivery 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: message header appears in the qmail system by  Daniel

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

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

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