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 delivered. 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 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" 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 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 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-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, patterns
are tried in the order as listed below:
· When the result has the form @otherdomain, the result becomes the same user in otherdomain.
· 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@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 propa‐
gated 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 expres‐
sions. 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 not available up to
and including Postfix version 2.4.
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 [email protected] by his ISP mail address, replaces [email protected] 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 protected] [email protected]
[email protected] [email protected]
@localdomain.local [email protected]
Execute the command "postmap /etc/postfix/generic" whenever the table is changed. Instead of hash, some sys‐
tems use dbm database files. To find out what tables your system supports use the command "postconf -m".
propagate_unmatched_extensions
A list of address rewriting or forwarding mechanisms that propagate an address extension from the orig‐
inal address to the result. Specify zero or more of canonical, virtual, alias, forward, include, or
generic.
Other parameters of interest:
inet_interfaces
The network interface addresses that this system receives mail on. You need to stop and start Postfix
when this parameter changes.
proxy_interfaces
Other interfaces that this machine receives mail on by way of a proxy agent or network address transla‐
tor.
mydestination
List of domains that this mail system considers local.
myorigin
The domain that is appended to locally-posted mail.
owner_request_special
Give special treatment to owner-xxx and xxx-request addresses.
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
GENERIC(5)
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