VIRTUAL(5)		      File Formats Manual		    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  recipi-
	      ent 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 result
	      When  pattern  matches  a mail 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 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 "unde-
	      liverable" to the often forged sender address.

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 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@vir-
       tual-alias.domain as undeliverable.

       Instead	of  specifying	the  virtual  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 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 bro-
       ken 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 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 2.4.

       Each  lookup operation uses the entire address once.  Thus, user@domain
       mail 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 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 propa-
	      gate  an	address	 extension  from  the  original address to the
	      result.  Specify zero or more of canonical, virtual, alias, for-
	      ward, 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



								    VIRTUAL(5)