Ubuntu Manpage: virtual - Postfix virtual domain mail delivery agent

Provided by: postfix_3.7.4-2build1_amd64

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_mailbox_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 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 mailbox 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 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 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 successful 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 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  problem cases, mail for an existing recipient is deferred and a warning is
       logged.

       Problems and transactions are logged to  syslogd(8)  or  postlogd(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 postmaster 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 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 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 the 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 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 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_mailbox_limit (51200000)
              The maximal size in bytes of an individual virtual(8) mailbox or maildir  file,  or
              zero (no limit).

       Implemented in the qmgr(8) daemon:

       virtual_destination_concurrency_limit ($default_destination_concurrency_limit)
              The  maximal  number of parallel deliveries to the same destination via the virtual
              message delivery transport.

       virtual_destination_recipient_limit ($default_destination_recipient_limit)
              The maximal number of recipients per  message  for  the  virtual  message  delivery
              transport.

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 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)
A prefix that is prepended to the process name in syslog records, so that, for
example, "smtpd" becomes "prefix/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 unsuccessful deliveries.

Available in Postfix version 3.3 and later:

enable_original_recipient (yes)
Enable support for the original recipient address after an address is rewritten to
a different address (for example with aliasing or with canonical mapping).

service_name (read-only)
The master.cf service name of a Postfix daemon process.

Available in Postfix 3.5 and later:

info_log_address_format (external)
The email address form that will be used in non-debug logging (info, warning,
etc.).

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(8postfix)