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 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.

MAILBOX LOCATION
       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:

	 $virtual_mailbox_base/$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" enve-
       lope  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 mail-
       box 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  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.

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  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.

SECURITY
       The  virtual(8) delivery agent is not security sensitive, provided that
       the lookup tables with recipient user/group  ID	information  are  ade-
       quately 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 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.

BUGS
       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.

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_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)
	      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 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  recipi-
	      ent.

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_concur-
       rency_limit)
	      The maximal number of parallel deliveries to the	same  destina-
	      tion via the virtual message delivery transport.

       virtual_destination_recipient_limit	 ($default_destination_recipi-
       ent_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 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  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.

       delay_logging_resolution_limit (2)
	      The maximal number of digits after the decimal point  when  log-
	      ging 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)
	      The mail system name that is prepended to the  process  name  in
	      syslog  records,	so  that  "smtpd" becomes, for example, "post-
	      fix/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
       andrewm@connect.com.au
       connect.com.au Pty. Ltd.
       Level 3, 213 Miller St
       North Sydney 2060, NSW, Australia



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