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VIRTUAL(8postfix)                                                                  VIRTUAL(8postfix)



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-of‐
       fice  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  con‐
       figuration  parameters (see below).  The virtual_mailbox_maps table is indexed by the recipi‐
       ent 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 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(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 de‐
       livery 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 nu‐
       merical 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.

CASE FOLDING
       All  delivery  decisions are made using the full recipient address, folded to lower case. See
       also the next section for a few exceptions with optional address extensions.

TABLE SEARCH ORDER
       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 successful lookup.

       •      When the recipient has an optional address extension the user+extension AT domain.tld ad‐
              dress is looked up first.

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

       •      The user AT domain.tld 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  expressions. In that case, only the full recipient address is given to the regu‐
       lar-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) or postlogd(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 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 inconvenience 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  lim‐
       ited 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_mailbox_maps (empty)
              Optional  lookup  tables  with  all  valid  addresses  in the domains that match $vir‐
              tual_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)
              Postfix is final destination for the specified list of domains; mail is delivered  via
              the $virtual_transport mail delivery transport.

       virtual_transport (virtual)
              The default mail delivery transport and next-hop destination for final delivery to do‐
              mains 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_mailbox_limit (51200000)
              The maximal size in bytes of an individual virtual(8) mailbox or maildir file, or zero
              (no limit).

       Implemented in the qmgr(8) daemon:

       virtual_destination_concurrency_limit ($default_destination_concurrency_limit)
              The maximal number of parallel deliveries to the same destination via the virtual mes‐
              sage delivery transport.

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

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 ter‐
              minated 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)
              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  an  incoming
              connection before terminating voluntarily.

       max_use (100)
              The  maximal number of incoming connections that a Postfix daemon process will service
              before terminating voluntarily.

       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 (see 'postconf -d' output)
              A prefix that is prepended to the process name in syslog records, so that,  for  exam‐
              ple, "smtpd" becomes "prefix/smtpd".

       Available in Postfix version 3.0 and later:

       virtual_delivery_status_filter ($default_delivery_status_filter)
              Optional  filter  for the virtual(8) delivery agent to change the delivery status code
              or explanatory text of successful or unsuccessful deliveries.

       Available in Postfix version 3.3 and later:

       enable_original_recipient (yes)
              Enable support for the original recipient address after an address is rewritten  to  a
              different address (for example with aliasing or with canonical mapping).

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

       Available in Postfix 3.5 and later:

       info_log_address_format (external)
              The email address form that will be used in non-debug logging (info, warning, etc.).

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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

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



                                                                                   VIRTUAL(8postfix)