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VIRTUAL(5)                                                          VIRTUAL(5)



NAME
       virtual(5,8) - Postfix virtual(5,8) alias table format

SYNOPSIS
       postmap /etc/postfix/virtual(5,8)

       postmap -q "string(3,n)" /etc/postfix/virtual(5,8)

       postmap -q - /etc/postfix/virtual(5,8) <inputfile

DESCRIPTION
       The  optional  virtual(5,8)(5)  alias table rewrites recipient addresses for
       all local, virtual(5,8) and remote mail(1,8) destinations.  This  is  unlike  the
       aliases(5)  table  which  is  used only for local(8) delivery.  Virtual
       aliasing is recursive, and is implemented  by  the  Postfix  cleanup(8)
       daemon before mail(1,8) is queued.

       The main applications of virtual(5,8) aliasing are:

             To redirect mail(1,8) for one address to one or more addresses.

             To  implement  virtual(5,8)  alias  domains  where  all addresses are
              aliased to addresses in(1,8) other domains.

              Virtual alias domains are not to be confused  with  the  virtual(5,8)
              mailbox domains that are implemented with the Postfix virtual(5,8)(8)
              mail(1,8) delivery agent. With virtual(5,8) mailbox domains, each  recipi-
              ent 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(7,n,1 builtins)  S0,  if(3,n)  you
       like. Use canonical(5) mapping to rewrite header and envelope addresses
       in(1,8) general.

       Normally, the virtual(5,8)(5) alias table is specified as a text  file(1,n)  that
       serves as input to the postmap(1) command.  The result, an indexed file(1,n)
       in(1,8) dbm or db format, is used for fast searching  by  the  mail(1,8)  system.
       Execute  the command "postmap /etc/postfix/virtual(5,8)" in(1,8) order to rebuild
       the indexed file(1,n) 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  expressions,  or  lookups  can  be
       directed  to  TCP-based server. In that case, the lookups are done in(1,8) 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(1,8) address, replace it by the corre-
              sponding 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 logical 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(1,8) the order as
       listed below:

       user@domain address, address, ...
              Redirect mail(1,8) for user@domain to address.   This  form  has  the
              highest precedence.

       user address, address, ...
              Redirect  mail(1,8)  for  user@site  to address when site is equal to
              $myorigin, when site is listed in(1,8) $mydestination, or when it  is
              listed in(1,8) $inet_interfaces or $proxy_interfaces.

              This  functionality  overlaps  with  functionality  of the local
              aliases(5) database. The difference is that  virtual(5,8)(5)  mapping
              can be applied to non-local addresses.

       @domain address, address, ...
              Redirect  mail(1,8)  for other users(1,5) in(1,8) domain to address.  This form
              has the lowest precedence.

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

             When the result has the form @otherdomain,  the  result  becomes
              the  same  user  in(1,8)  otherdomain.  This works only for the first
              address in(1,8) a multi-address lookup result.

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

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

ADDRESS EXTENSION
       When a mail(1,8) address localpart contains the optional recipient 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 propagated to the result of table
       lookup.

VIRTUAL ALIAS DOMAINS
       Besides virtual(5,8) aliases, the virtual(5,8) alias table can also  be  used  to
       implement  virtual(5,8)  alias  domains.  With  a  virtual(5,8) alias domain, all
       recipient addresses are aliased to addresses in(1,8) other domains.

       Virtual alias domains are not to be confused with the  virtual(5,8)  mailbox
       domains  that are implemented with the Postfix virtual(5,8)(8) mail(1,8) delivery
       agent. With virtual(5,8) mailbox domains, each recipient  address  can  have
       its own mailbox.

       With  a  virtual(5,8) alias domain, the virtual(5,8) domain has its own user name
       space. Local (i.e. non-virtual) usernames are not visible in(1,8) a  virtual(5,8)
       alias  domain.  In particular, local aliases(5) and local mailing lists
       are not visible as localname@virtual-alias.domain.

       Support for a virtual(5,8) alias domain looks like:

       /etc/postfix/main.cf:
           virtual_alias_maps = hash:/etc/postfix/virtual(5,8)

           Note: some systems use dbm databases instead of hash.  See the out-
           put from "postconf(1,5) -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(5,8) alias
       domain. Without  this  entry,  mail(1,8)  is  rejected  with  "relay  access(2,5)
       denied", or bounces with "mail(1,8) loops back to myself".

       Do  not specify virtual(5,8) alias domain names in(1,8) the main.cf mydestination
       or relay_domains configuration parameters.

       With a virtual(5,8) alias domain, the Postfix SMTP server accepts  mail(1,8)  for
       known-user@virtual-alias.domain, and rejects mail(1,8) for unknown-user@vir-
       tual-alias.domain as undeliverable.

       Instead of specifying the  virtual(5,8)  alias  domain  name  via  the  vir-
       tual_alias_maps  table,  you  may  also specify it via the main.cf vir-
       tual_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(1,8) 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(1,8) addresses are not  bro-
       ken  up  into their user and @domain constituent parts, nor is user+foo
       broken up into user and foo.

       Patterns are applied in(1,8) the order as specified in(1,8) the  table,  until  a
       pattern is found that matches the search string.

       Results  are the same as with indexed file(1,n) lookups, with the additional
       feature that parenthesized substrings from the pattern can be  interpo-
       lated 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  description  of  the   TCP
       client/server  lookup  protocol, see tcp_table(5).  This feature is not
       available up to and including Postfix version(1,3,5) 2.2.

       Each lookup operation uses the entire address once.  Thus,  user@domain
       mail(1,8)  addresses  are  not  broken  up  into their user and @domain con-
       stituent parts, nor is user+foo broken up into user and foo.

       Results are the same as with indexed file(1,n) 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(1,n) for syntax details and for default values.
       Use the "postfix reload" command after a configuration change.

       virtual_alias_maps
              List of virtual(5,8) aliasing tables.

       virtual_alias_domains
              List of virtual(5,8) alias domains. This uses the same syntax as  the
              mydestination parameter.

       propagate_unmatched_extensions
              A list of address rewriting or forwarding mechanisms that propa-
              gate an address extension  from  the  original  address  to  the
              result.  Specify zero or more of canonical, virtual(5,8), alias, for-
              ward, include, or generic.

       Other parameters of interest:

       inet_interfaces
              The network interface addresses that this system  receives  mail(1,8)
              on.   You  need  to  stop  and start Postfix when this parameter
              changes.

       mydestination
              List of domains that this mail(1,8) 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(1,8) on by way of a
              proxy agent or network address translator.

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

README FILES
       Use "postconf(1,5) readme_directory" or "postconf(1,5) html_directory" to  locate
       this information.
       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)

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