bionic (5) virtual.5.gz

Provided by: postfix_3.3.0-1ubuntu0.4_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.

       With lookups from indexed files such as DB or DBM, or from networked tables such as  NIS,  LDAP  or  SQL,
       each user@domain query produces a sequence of query patterns as described below.

       Each  query  pattern is sent to each specified lookup table before trying the next query pattern, until a
       match is found.

       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)