man > generic(5)

GENERIC(5)                               File Formats Manual                              GENERIC(5)

NAME
       generic - Postfix generic table format

SYNOPSIS
       postmap /etc/postfix/generic

       postmap -q "string" /etc/postfix/generic

       postmap -q - /etc/postfix/generic <inputfile

DESCRIPTION
       The  optional  generic(5) table specifies an address mapping that applies when mail is deliv‐
       ered. This is the opposite of canonical(5) mapping, which applies when mail is received.

       Typically, one would use the generic(5) table on a system that does not have a valid Internet
       domain name and that uses something like localdomain.local instead.  The generic(5) table  is
       then  used  by  the smtp(8) client to transform local mail addresses into valid Internet mail
       addresses when mail has to be sent across the Internet.  See the EXAMPLE section at  the  end
       of this document.

       The  generic(5) mapping affects both message header addresses (i.e. addresses that appear in‐
       side messages) and message envelope addresses (for example, the addresses that  are  used  in
       SMTP protocol commands).

       Normally,  the  generic(5)  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/generic" 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 cases, 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 result
              When pattern matches a mail address, replace it by the corresponding result.

       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
              Replace user@domain by address. This form has the highest precedence.

       user address
              Replace  user@site  by address when site is equal to $myorigin, when site is listed in
              $mydestination, or when it is listed in $inet_interfaces or $proxy_interfaces.

       @domain address
              Replace other addresses in domain by address.  This form has the lowest precedence.

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.

       •      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 table lookup.

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.

EXAMPLE
       The  following  shows  a generic mapping with an indexed file.  When mail is sent to a remote
       host via SMTP, this replaces his AT localdomain.local by his ISP mail address, replaces  her@lo‐
       caldomain.local  by  her  ISP mail address, and replaces other local addresses by his ISP ac‐
       count, with an address extension of +local (this example assumes that the  ISP  supports  "+"
       style address extensions).

       /etc/postfix/main.cf:
           smtp_generic_maps = hash:/etc/postfix/generic

       /etc/postfix/generic:
           his AT localdomain.local   hisaccount AT hisisp.example
           her AT localdomain.local   heraccount AT herisp.example
           @localdomain.local      hisaccount+local AT hisisp.example

       Execute the command "postmap /etc/postfix/generic" whenever the table is changed.  Instead of
       hash,  some  systems use dbm database files. To find out what tables your system supports use
       the command "postconf -m".

BUGS
       The table format does not understand quoting conventions.

CONFIGURATION PARAMETERS
       The following main.cf parameters are especially relevant.  The text below provides only a pa‐
       rameter summary. See postconf(5) for more details including examples.

       smtp_generic_maps (empty)
              Optional lookup tables that perform address rewriting in the Postfix SMTP client, typ‐
              ically to transform a locally valid address into a globally valid address when sending
              mail across the Internet.

       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.

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

       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 "-".

SEE ALSO
       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters
       smtp(8), Postfix SMTP client

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
       STANDARD_CONFIGURATION_README, configuration examples

LICENSE
       The Secure Mailer license must be distributed with this software.

HISTORY
       A genericstable feature appears in the Sendmail MTA.

       This feature is available in Postfix 2.2 and later.

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

                                                                                          GENERIC(5)