    VIRTUAL(5)                                                          VIRTUAL(5)

    NAME
           virtual - Postfix virtual alias table format

    SYNOPSIS
           postmap /etc/postfix/virtual

           postmap -q "string" /etc/postfix/virtual

           postmap -q - /etc/postfix/virtual <inputfile

    DESCRIPTION
           The  optional  virtual(5)  alias  table  specifies address
           aliasing  for  arbitrary  local  or  non-local   recipient
           addresses.  Virtual  aliasing is recursive, and is done by
           the Postfix cleanup(8) daemon.

           The main applications of virtual aliasing are:

           o      To redirect mail for one address  to  one  or  more
                  addresses.

           o      To   implement  virtual  alias  domains  where  all
                  addresses  are  aliased  to  addresses   in   other
                  domains.

                  Virtual  alias  domains are not to be confused with
                  the virtual mailbox domains  that  are  implemented
                  with  the  Postfix  virtual(8) mail delivery agent.
                  With  virtual  mailbox  domains,   each   recipient
                  address can have its own mailbox.

           Virtual  aliasing  is  applied  only to recipient envelope
           addresses, and does not  affect  message  headers.   Think
           Sendmail  rule  set S0, if you like. Use canonical(5) map-
           ping to rewrite header and envelope addresses in  general.

           Normally,  the  virtual(5)  alias  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. Execute the command
           "postmap  /etc/postfix/virtual"  in  order  to rebuild the
           indexed file after changing the text file.

           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, the table can be  provided  as  a  regular-
           expression map where patterns are given as regular expres-
           sions, or lookups can be directed to TCP-based server.  In
           that  case,  the  lookups are done in a slightly different
           way as described below under "REGULAR  EXPRESSION  TABLES"
           and "TCP-BASED TABLES".

    TABLE FORMAT
           The input format for the postmap(1) command is as follows:

           pattern result
                  When pattern matches a mail address, replace it  by
                  the corresponding result.

           blank lines and comments
                  Empty  lines and whitespace-only lines are ignored,
                  as are lines whose first  non-whitespace  character
                  is a `#'.

           multi-line text
                  A  logical  line starts with non-whitespace text. A
                  line that starts with whitespace continues a  logi-
                  cal line.

    TABLE SEARCH ORDER
           With lookups from indexed files such as DB or DBM, or from
           networked tables such as NIS, LDAP or  SQL,  patterns  are
           tried in the order as listed below:

           user@domain address, address, ...
                  Redirect  mail  for  user@domain  to address.  This
                  form has the highest precedence.

           user address, address, ...
                  Redirect mail for user@site to address when site is
                  equal  to $myorigin, when site is listed in $mydes-
                  tination, or when it is listed in  $inet_interfaces
                  or $proxy_interfaces.

                  This  functionality  overlaps with functionality of
                  the local aliases(5) database.  The  difference  is
                  that virtual(5) mapping can be applied to non-local
                  addresses.

           @domain address, address, ...
                  Redirect mail for other users in domain to address.
                  This form has the lowest precedence.

    RESULT ADDRESS REWRITING
           The lookup result is subject to address rewriting:

           o      When  the  result  has  the  form @otherdomain, the
                  result becomes the same user in otherdomain.   This
                  works only for the first address in a multi-address
                  lookup result.

           o      When "append_at_myorigin=yes", append  "@$myorigin"
                  to addresses without "@domain".

           o      When "append_dot_mydomain=yes", append ".$mydomain"
                  to addresses without ".domain".

    ADDRESS EXTENSION
           When a mail address localpart contains the optional recip-
           ient  delimiter  (e.g., user+foo@domain), the lookup order
           becomes: user+foo@domain, user@domain, user+foo, user, and
           @domain.

           The   propagate_unmatched_extensions   parameter  controls
           whether an unmatched address extension  (+foo)  is  propa-
           gated to the result of table lookup.

    VIRTUAL ALIAS DOMAINS
           Besides  virtual aliases, the virtual alias table can also
           be used to implement virtual alias domains. With a virtual
           alias  domain,  all  recipient  addresses  are  aliased to
           addresses in other domains.

           Virtual alias domains are not to be confused with the vir-
           tual mailbox domains that are implemented with the Postfix
           virtual(8)  mail  delivery  agent.  With  virtual  mailbox
           domains,  each recipient address can have its own mailbox.

           With a virtual alias domain, the virtual  domain  has  its
           own  user  name  space. Local (i.e. non-virtual) usernames
           are not visible in a virtual alias domain. In  particular,
           local  aliases(5)  and local mailing lists are not visible
           as localname@virtual-alias.domain.

           Support for a virtual alias domain looks like:

           /etc/postfix/main.cf:
               virtual_alias_maps = hash:/etc/postfix/virtual

               Note: some systems use dbm databases instead of  hash.
               See  the output from "postconf -m" for available data-
               base types.

           /etc/postfix/virtual:
               virtual-alias.domain anything (right-hand content does not matter)
               postmaster@virtual-alias.domain      postmaster
               user1@virtual-alias.domain   address1
               user2@virtual-alias.domain   address2, address3

           The virtual-alias.domain anything entry is required for  a
           virtual alias domain. Without this entry, mail is rejected
           with "relay access denied", or bounces  with  "mail  loops
           back to myself".

           Do  not  specify virtual alias domain names in the main.cf
           mydestination or relay_domains configuration parameters.

           With a virtual  alias  domain,  the  Postfix  SMTP  server
           accepts   mail  for  known-user@virtual-alias.domain,  and
           rejects  mail  for  unknown-user@virtual-alias.domain   as
           undeliverable.

           Instead  of  specifying  the virtual alias domain name via
           the virtual_alias_maps table, you may also specify it  via
           the main.cf virtual_alias_domains configuration parameter.
           This latter parameter uses the same syntax as the  main.cf
           mydestination configuration parameter.

    REGULAR EXPRESSION TABLES
           This  section  describes how the table lookups change when
           the table is given in the form of regular expressions. For
           a  description  of regular expression lookup table syntax,
           see regexp_table(5) or pcre_table(5).

           Each pattern is a regular expression that  is  applied  to
           the entire address being looked up. Thus, user@domain mail
           addresses are not broken up into their  user  and  @domain
           constituent parts, nor is user+foo broken up into user and
           foo.

           Patterns are applied in the order as specified in the  ta-
           ble,  until  a  pattern  is  found that matches the search
           string.

           Results are the same as with indexed  file  lookups,  with
           the  additional feature that parenthesized substrings from
           the pattern can be interpolated as $1, $2 and so on.

    TCP-BASED TABLES
           This section describes how the table lookups  change  when
           lookups are directed to a TCP-based server. For a descrip-
           tion of the TCP client/server lookup protocol, see tcp_ta-
           ble(5).  This feature is not available up to and including
           Postfix version 2.2.

           Each lookup operation uses the entire address once.  Thus,
           user@domain  mail  addresses  are not broken up into their
           user and @domain constituent parts, nor is user+foo broken
           up into user and foo.

           Results are the same as with indexed file lookups.

    BUGS
           The  table format does not understand quoting conventions.

    CONFIGURATION PARAMETERS
           The following main.cf parameters are  especially  relevant
           to  this  topic.  See  the Postfix main.cf file for syntax
           details and for default values. Use the  "postfix  reload"
           command after a configuration change.

           virtual_alias_maps
                  List of virtual aliasing tables.

           virtual_alias_domains
                  List  of  virtual alias domains. This uses the same
                  syntax as the mydestination parameter.

           propagate_unmatched_extensions
                  A list of address rewriting  or  forwarding  mecha-
                  nisms  that propagate an address extension from the
                  original address to the result.   Specify  zero  or
                  more   of   canonical,   virtual,  alias,  forward,
                  include, or generic.

           Other parameters of interest:

           inet_interfaces
                  The network interface addresses  that  this  system
                  receives mail on.  You need to stop and start Post-
                  fix when this parameter changes.

           mydestination
                  List of domains that  this  mail  system  considers
                  local.

           myorigin
                  The  domain  that  is  appended to any address that
                  does not have a domain.

           owner_request_special
                  Give special treatment to owner-xxx and xxx-request
                  addresses.

           proxy_interfaces
                  Other interfaces that this machine receives mail on
                  by way of a proxy agent or network address transla-
                  tor.

    SEE ALSO
           cleanup(8), canonicalize and enqueue mail
           postmap(1), Postfix lookup table manager
           postconf(5), configuration parameters
           canonical(5), canonical address mapping

    README FILES
           DATABASE_README, Postfix lookup table overview
           ADDRESS_REWRITING_README, address rewriting guide
           VIRTUAL_README, domain hosting guide

    LICENSE
           The Secure Mailer license must be  distributed  with  this
           software.

    AUTHOR(S)
           Wietse Venema
           IBM T.J. Watson Research
           P.O. Box 704
           Yorktown Heights, NY 10598, USA

                                                                        VIRTUAL(5)