GENERICS(5) GENERICS(5)
NAME
generics - Postfix generics table format
SYNOPSIS
postmap /etc/postfix/generics
postmap -q "string" /etc/postfix/generics
postmap -q - /etc/postfix/generics <inputfile
DESCRIPTION
The optional generics(5) table specifies an address map-
ping 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 generics(5) table on a system
that does not have a valid Internet domain name and that
uses something like localdomain.local instead. The gener-
ics(5) table is then used by the smtp(8) client to trans-
form 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 generics(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 generics(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/generics" 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 expres-
sions, 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".
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 logi-
cal 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:
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
$proxy_interfaces.
@domain address
Replace other addresses in domain by address. This
form has the lowest precedence.
RESULT ADDRESS REWRITING
The lookup result is subject to address rewriting:
o When the result has the form @otherdomain, the
result becomes the same user in otherdomain.
o When "append_at_myorigin=yes", append "@$myorigin"
to addresses without "@domain".
o When "append_dot_mydomain=yes", append ".$mydomain"
to addresses without ".domain".
ADDRESS EXTENSION
When a mail address localpart contains the optional recip-
ient 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 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.
TCP-BASED TABLES
This section describes how the table lookups change when
lookups are directed to a TCP-based server. For a descrip-
tion of the TCP client/server lookup protocol, see
tcp_table(5). This feature is not available up to and
including Postfix version 2.2.
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@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_generics_maps = hash:/etc/postfix/generics
/etc/postfix/generics:
his@localdomain.local hisaccount@hisisp.example
her@localdomain.local heraccount@herisp.example
@localdomain.local hisaccount+local@hisisp.example
Execute the command "postmap /etc/postfix/generics" when-
ever the table is changed. Instead of hash, some systems
use dbm database files. To find out what tables your sys-
tem 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 parameter summary. See
postconf(5) for more details including examples.
smtp_generics_maps
Address mapping lookup table for envelope and
header sender and recipient addresses while deliv-
ering mail via SMTP.
propagate_unmatched_extensions
A list of address rewriting or forwarding mecha-
nisms that propagate an address extension from the
original address to the result. Specify zero or
more of canonical, virtual, alias, forward,
include, or generics.
Other parameters of interest:
inet_interfaces
The network interface addresses that this system
receives mail on. You need to stop and start Post-
fix 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
DATABASE_README, Postfix lookup table overview
ADDRESS_REWRITING_README, address rewriting guide
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
GENERICS(5)