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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(8)  delivery agent is designed for virtual mail hosting services. 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.

MAILBOX LOCATION
       The mailbox location is controlled by the virtual_mailbox_base and virtual_mailbox_maps configuration  parame‐
       ters (see below).  The virtual_mailbox_maps table is indexed by the recipient address as described under TABLE
       SEARCH ORDER below.

       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  format.    This  format
       stores multiple messages in one textfile.

       The  virtual(8) 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: 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 problems, 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(8) delivery agent prepends a Delivered-To:  message  header  with  the  final  envelope  recipient
       address,  prepends  an  X-Original-To:  header  with the recipient address as given to Postfix, and prepends a
       Return-Path: message header with the envelope sender address.

       By definition, maildir format does  not  require  application-level  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,  respec‐
       tively.

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


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

       ·      The [email protected] address, without address extension, is looked up next.

       ·      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 expres‐
       sions. In that case, only the full recipient address is given to the regular-expression map.

SECURITY
       The  virtual(8)  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.

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

       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 delivery agent will terminate  with  a  fatal
       error.

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 man‐
       ager 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 supports address extensions in email addresses and in lookup  table  keys,  but  does  not
       propagate address extension information to the result of table lookup.

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

CONFIGURATION PARAMETERS
       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.

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

       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)
              Postfix is final destination for the specified list  of  domains;  mail  is  delivered  via  the  $vir‐
              tual_transport mail delivery transport.

       virtual_transport (virtual)
              The  default mail delivery transport and next-hop destination for final delivery to domains listed with
              $virtual_mailbox_domains.

       Available in Postfix version 2.5.3 and later:

       strict_mailbox_ownership (yes)
              Defer delivery when a mailbox file is not owned by its recipient.

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

       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 removed.

RESOURCE AND RATE CONTROLS
       virtual_destination_concurrency_limit ($default_destination_concurrency_limit)
              The maximal number of parallel deliveries to the same destination  via  the  virtual  message  delivery
              transport.

       virtual_destination_recipient_limit ($default_destination_recipient_limit)
              The maximal number of recipients per message for the virtual message delivery transport.

       virtual_mailbox_limit (51200000)
              The maximal size in bytes of an individual virtual(8) mailbox or maildir file, or zero (no limit).

MISCELLANEOUS CONTROLS
       config_directory (see 'postconf -d' output)
              The default location of the Postfix main.cf and master.cf configuration 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.

       delay_logging_resolution_limit (2)
              The maximal number of digits after the decimal point when logging sub-second delay values.

       ipc_timeout (3600s)

       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 (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".

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

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

LICENSE
       The Secure Mailer license must be distributed with this software.

HISTORY
       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 Bernstein.

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

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

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



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