man > virtual(5)

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. This feature is implemented in the Postfix cleanup(8) daemon  before  mail
       is queued.

       Virtual  aliasing is recursive; to terminate recursion for a specific address, alias that ad‐
       dress to itself.

       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 do‐
              mains, 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 a TCP-based server. In those case,  the
       lookups are done in a slightly different way as described below under "REGULAR EXPRESSION TA‐
       BLES" 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-white‐
              space 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, 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  pat‐
       tern, 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_inter‐
              faces.

              This  functionality  overlaps with the 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  prece‐
              dence.

              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-exis‐
              tent  recipients  and  then  tries to return that mail as "undeliverable" to the often
              forged sender address.

              To avoid backscatter with mail for a wild-card domain, replace the  wild-card  mapping
              with  explicit 1:1 mappings, or add a reject_unverified_recipient restriction for that
              domain:

                  smtpd_recipient_restrictions =
                      ...
                      reject_unauth_destination
                      check_recipient_access
                          inline:{example.com=reject_unverified_recipient}
                  unverified_recipient_reject_code = 550

              In the above example, Postfix may contact a remote server if the recipient is  aliased
              to a remote 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 other‐
              domain.  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@do‐
       main), 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 a 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 imple‐
       mented 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 AT 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 AT virtual-alias.domain postmaster
           user1 AT virtual-alias.domain      address1
           user2 AT 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 my‐
       self".

       Do not specify virtual alias domain names in the main.cf mydestination or relay_domains  con‐
       figuration parameters.

       With  a  virtual  alias  domain,  the  Postfix  SMTP  server accepts mail for known-user@vir‐
       tual-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  reg‐
       exp_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 parenthe‐
       sized 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 available in Postfix 2.5 and later.

       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  af‐
       ter a configuration change.

       virtual_alias_maps ($virtual_maps)
              Optional lookup tables that alias specific mail addresses or domains to other local or
              remote addresses.

       virtual_alias_domains ($virtual_alias_maps)
              Postfix is the final destination for the specified list of virtual alias domains, that
              is,  domains for which all addresses are aliased to addresses in other local or remote
              domains.

       propagate_unmatched_extensions (canonical, virtual)
              What address lookup tables copy an address extension from the lookup key to the lookup
              result.

       Other parameters of interest:

       inet_interfaces (all)
              The network interface addresses that this mail system receives mail on.

       mydestination ($myhostname, localhost.$mydomain, localhost)
              The list of domains that are delivered via the $local_transport mail  delivery  trans‐
              port.

       myorigin ($myhostname)
              The domain name that locally-posted mail appears to come from, and that locally posted
              mail is delivered to.

       owner_request_special (yes)
              Enable  special treatment for owner-listname entries in the aliases(5) file, and don't
              split owner-listname and listname-request address localparts when the recipient_delim‐
              iter is set to "-".

       proxy_interfaces (empty)
              The network interface addresses that this mail system receives mail on  by  way  of  a
              proxy or network address translation unit.

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

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