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 localdo‐
main.local instead. The generic(5) table is then used by the smtp(8)
client to transform local mail addresses into valid Internet mail ad‐
dresses 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. ad‐
dresses 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 to create an indexed file for fast
lookup.
Execute the command "postmap /etc/postfix/generic" to rebuild a de‐
fault-type indexed file after changing the text file, or execute
"postmap type:/etc/postfix/generic" to specify an explicit type.
The default indexed file type is configured with the default_data‐
base_type parameter. Depending on the platform this may be one of
lmdb:, cdb:, hash:, or dbm: (without the trailing ':').
When the table is provided via other means such as NIS, LDAP or SQL,
the same lookups are done as for ordinary indexed files. Managing such
databases is outside the scope of Postfix.
Alternatively, the table can be provided as a regular-expression map
where patterns are given as regular expressions, or lookups can be di‐
rected 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 corre‐
sponding 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, each user@domain query produces a se‐
quence 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
Replace user@domain by address. This form has the highest prece‐
dence.
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 $proxy_interfaces.
@domain address
Replace other addresses in domain by address. This form has the
lowest precedence.
RESULT ADDRESS REWRITING
The lookup result is subject to address rewriting:
• When the result has the form @otherdomain, the result becomes
the same user in otherdomain.
• When "append_at_myorigin=yes", append "@$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 un‐
matched 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 regexp_table(5) or pcre_table(5).
Each pattern is a regular expression that is applied to the entire ad‐
dress being looked up. Thus, user@domain mail addresses are not broken
up into their user and @domain constituent parts, nor is user+foo bro‐
ken 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 interpo‐
lated 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 con‐
stituent 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@localdomain.local 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:
his@localdomain.local hisaccount@hisisp.example
her@localdomain.local heraccount@herisp.example
@localdomain.local hisaccount+local@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 be‐
low provides only a parameter 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, typically to transform a locally valid ad‐
dress 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 local network interface addresses that this mail system re‐
ceives mail on.
proxy_interfaces (empty)
The remote network interface addresses that this mail system re‐
ceives 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 $local_transport
mail delivery transport.
myorigin ($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-re‐
quest address localparts when the recipient_delimiter is set to
"-".
SEE ALSO
postmap(1), Postfix lookup table manager
postconf(5), configuration parameters
smtp(8), Postfix SMTP client
README FILES
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)