    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  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 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.

           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 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 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 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  an incoming connection
                  before terminating voluntarily.

           max_use (100)
                  The maximal number of incoming connections  that  a
                  Postfix  daemon  process will service before termi-
                  nating 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  direc-
                  tory.

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

                                                                        VIRTUAL(8)