Provided by: postfix_3.1.0-3_amd64 bug

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:

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

       ·      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" to
       rebuild an indexed file after changing the corresponding 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  those
       case,  the  lookups are done in a slightly different way as described below under "REGULAR
       EXPRESSION TABLES" or "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 address, address, ...
              When pattern matches a mail address, replace it by the corresponding address.

       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 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  $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(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.

              Note:  @domain is a wild-card. With this form, the Postfix SMTP server accepts mail
              for any recipient in domain, regardless of whether that recipient exists.  This may
              turn  your  mail  system  into a backscatter source: Postfix first accepts mail for
              non-existent recipients and then tries to return that mail  as  "undeliverable"  to
              the often forged sender address.

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
              otherdomain.  This works only for the  first  address  in  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  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 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 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.

       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  description  of  the  TCP  client/server  lookup  protocol,  see
       tcp_table(5).  This feature is not available up to and including Postfix version 2.4.

       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  mechanisms  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 Postfix 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 translator.

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

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       ADDRESS_REWRITING_README, address rewriting guide
       DATABASE_README, Postfix lookup table overview
       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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

                                                                                       VIRTUAL(5)