# man > generic(5) [_GENERIC_(5)](https://www.chedong.com/phpMan.php/man/GENERIC/5/markdown) File Formats Manual [_GENERIC_(5)](https://www.chedong.com/phpMan.php/man/GENERIC/5/markdown) ## 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)](https://www.chedong.com/phpMan.php/man/generic/5/markdown) table specifies an address mapping that applies when mail is deliv‐ ered. This is the opposite of [**canonical**(5)](https://www.chedong.com/phpMan.php/man/canonical/5/markdown) mapping, which applies when mail is received. Typically, one would use the [**generic**(5)](https://www.chedong.com/phpMan.php/man/generic/5/markdown) table on a system that does not have a valid Internet domain name and that uses something like _localdomain.local_ instead. The [**generic**(5)](https://www.chedong.com/phpMan.php/man/generic/5/markdown) table is then used by the [**smtp**(8)](https://www.chedong.com/phpMan.php/man/smtp/8/markdown) 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)](https://www.chedong.com/phpMan.php/man/generic/5/markdown) 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)](https://www.chedong.com/phpMan.php/man/generic/5/markdown) table is specified as a text file that serves as input to the [**postmap**(1)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown) 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)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown) 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)](https://www.chedong.com/phpMan.php/man/exptable/5/markdown) or [**pcre_table**(5)](https://www.chedong.com/phpMan.php/man/pcretable/5/markdown). 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)](https://www.chedong.com/phpMan.php/man/tcptable/5/markdown). 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@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: @localdomain.local hisaccount+ 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)](https://www.chedong.com/phpMan.php/man/postconf/5/markdown) 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)](https://www.chedong.com/phpMan.php/man/aliases/5/markdown) file, and don't split owner-_listname_ and _listname_-request address localparts when the recipient_delim‐ iter is set to "-". ## SEE ALSO [postmap(1)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown), Postfix lookup table manager [postconf(5)](https://www.chedong.com/phpMan.php/man/postconf/5/markdown), configuration parameters [smtp(8)](https://www.chedong.com/phpMan.php/man/smtp/8/markdown), 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)](https://www.chedong.com/phpMan.php/man/GENERIC/5/markdown)