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 (virtual_alias_maps) applies to all
       recipients: local(8), virtual, and remote.  This feature is implemented
       in the Postfix cleanup(8) daemon before mail is queued.

       This is unlike the aliases(5) table (alias_maps) which applies only to
       local(8) recipients.

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

       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
              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
       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, 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 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 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.

              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:

       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 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 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
       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 after a configuration change.

       virtual_alias_maps ($virtual_maps)
              Optional lookup tables with aliases that apply to all
              recipients: local(8), virtual, and remote; this is unlike
              alias_maps that apply only to local(8) recipients.

       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 local 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 transport.

       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_delimiter
              is set to "-".

       proxy_interfaces (empty)
              The remote 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

                                                                    VIRTUAL(5)