    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 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 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 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".

           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 unsuc-
                  cessful deliveries.

    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

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

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

                                                                        VIRTUAL(8)