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VIRTUAL(8)                                                          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_mail-
       box_base and virtual_mailbox_maps configuration parameters
       (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 recip-
       ient  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 deliv-
       ered  in qmail maildir format. This format stores one mes-
       sage 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  applica-
       tion-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, respectively.

       The virtual_minimum_uid parameter imposes a lower bound on
       numerical user ID values that may be specified in any vir-
       tual_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 search-
       ing by the mail system.

       The search order is as follows. The search stops upon  the
       first successful lookup.

       o      When  the  recipient has an optional address exten-
              sion  the  [email protected]   address   is
              looked up first.

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

       o      The [email protected] address, without address exten-
              sion, 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 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).   Cor-
       rupted  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 trou-
       ble.

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 vir-
       tual(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  $vir-
              tual_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  $vir-
              tual_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  $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.

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 exclu-
              sive 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_destina-
       tion_concurrency_limit)
              The maximal number of parallel  deliveries  to  the
              same  destination  via the virtual message delivery
              transport.

       virtual_destination_recipient_limit     ($default_destina-
       tion_recipient_limit)
              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).

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)
              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 daemon 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  direc-
              tory.

       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, "postfix/smtpd".

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

README_FILES
       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 sys-
       tem 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

                                                                    VIRTUAL(8)