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. In that case, the lookups are done  in  a  slightly
       different way as described below.
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.
              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.  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.
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.
       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.
SEE ALSO
       cleanup(8) canonicalize and enqueue mail
       postmap(1) create mapping table
       regexp_table(5) POSIX regular expression table format
       pcre_table(5) Perl Compatible Regular Expression table format
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)