Provided by: postfix_3.1.0-3ubuntu0.4_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)