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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 rewrites recipient
       addresses for all local, all virtual, and all remote  mail
       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 is queued.

       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.   Use
       canonical(5)   mapping  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".

CASE FOLDING
       The search string is folded to lowercase  before  database
       lookup.  As  of Postfix 2.3, the search string is not case
       folded with database types such as regexp: or pcre:  whose
       lookup fields can match both upper and lower case.

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 [email protected].

       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)
           [email protected]      postmaster
           [email protected]   address1
           [email protected]   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  [email protected],  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, [email protected] 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 2.3.

       Each lookup operation uses the entire address once.  Thus,
       [email protected]  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)