    VIRTUAL(5)                                             VIRTUAL(5)

    NAME
           virtual - format of Postfix virtual alias table

    SYNOPSIS
           postmap /etc/postfix/virtual

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

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

    DESCRIPTION
           The  optional virtual alias table specifies address alias-
           ing 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 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.

           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, ...
                  Mail  for  user@domain  is  redirected  to address.
                  This form has the highest precedence.

           user address, address, ...
                  Mail for user@site is redirected  to  address  when
                  site  is equal to $myorigin, when site is listed in
                  $mydestination,   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  mapping  can be applied to non-local
                  addresses.

           @domain address, address, ...
                  Mail for  any  user  in  domain  is  redirected  to
                  address.  This form has the lowest precedence.

           In  all the above forms, when address has the form @other-
           domain, the result is the same user in otherdomain.   This
           works for the first address in the expansion only.

    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 database
               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
           table, 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_table(5).  This feature is not  available  in  Postfix
           version 2.1.

           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,  or
                  include.

           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)