virtual



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.


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.

       ·      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.

       ·      The  user@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 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 for domains that match the
              $virtual_mailbox_domains parameter value.


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 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 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.

       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 dae-
              mon 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 directory.

       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, "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



                                                                    VIRTUAL(8)

Man(1) output converted with man2html