postmap /etc/postfix/generic postmap -q "string" /etc/postfix/generic postmap -q - /etc/postfix/generic <inputfile
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 inside 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" in order to rebuild the indexed file after changing the 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 that case, the lookups are done in a slightly different way as described below under "REGULAR EXPRESSION TABLES" and "TCP-BASED TABLES".
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.
The input format for the postmap(1) command is as follows:
With lookups from indexed files such as DB or DBM, or from networked tables such as NIS, LDAP or SQL, patterns are tried in the order as listed below:
The lookup result is subject to address rewriting:
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.
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.
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 2.3.
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.
The following shows a generic mapping with an indexed file. When mail is sent to a remote host via SMTP, this replaces email@example.com by his ISP mail address, replaces firstname.lastname@example.org by her ISP mail address, and replaces other local addresses by his ISP account, 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: email@example.com firstname.lastname@example.org email@example.com firstname.lastname@example.org @localdomain.local email@example.comExecute 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".
The following main.cf parameters are especially relevant. The text below provides only a parameter summary. See postconf(5) for more details including examples.
Other parameters of interest:
postmap(1), Postfix lookup table manager postconf(5), configuration parameters smtp(8), Postfix SMTP client
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
The Secure Mailer license must be distributed with this software.
A genericstable feature appears in the Sendmail MTA. This feature is available in Postfix 2.2 and later.
Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA