REGEXP_TABLE(5)

NAME
regexp_table - format of Postfix regular expression tables

SYNOPSIS
regexp:/etc/postfix/filename

DESCRIPTION
The Postfix mail system uses optional tables for address rewriting or mail routing. These tables are usually in dbm or db format. Alternatively, lookup tables can be specified in POSIX regular expression form. To find out what types of lookup tables your Postfix system supports use the postconf -m command. The general form of a Postfix regular expression table is:

blanks and comments
    Blank lines are ignored, as are lines beginning with `#'.

leading whitespace
    Lines that begin with whitespace continue the previous line.

pattern result
    When pattern matches a search string, use the corresponding result. A line that starts with white space continues the preceding line.

pattern1!pattern2 result
    Matches pattern1 but not pattern2.

Each pattern is a regular expression enclosed by a pair of delimiters. The regular expression syntax is described in re_format(7). The expression delimiter can be any character, except whitespace or characters that have special meaning (traditionally the forward slash is used). The regular expression can contain whitespace. By default, matching is case-insensitive, although following the second slash with an `i' flag will reverse this. Other flags are `x' (disable extended expression syntax), and `m' (enable multi-line mode). Each pattern is applied to the entire string being looked up. Depending on the application, that string is an entire client hostname, an entire client IP address, or an entire mail address. Thus, no parent domain or parent network search is done, and 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. Substitution of sub-strings from the matched expression is possible using $1, $2, etc.. The macros in the replacement string may need to be written as ${n} or $(n) if they aren't followed by whitespace.

EXAMPLES
# Disallow sender-specified routing. This is a must if you relay mail
# for other domains.
/[%!@].*[%!@]/            550 Sender-specified routing rejected
# Postmaster is OK, that way they can talk to us about how to fix
# their problem.
/^postmaster@.*$/         OK
# Protect your outgoing majordomo exploders
/^(.*)-outgoing@(.*)$/!/^owner-.*/      550 Use ${1}@${2} instead

SEE ALSO
pcre_table(5) format of PCRE tables

AUTHOR(S)
The regexp table lookup code was originally written by:
LaMont Jones
lamont@hp.com
That code was based on the PCRE dictionary contributed by:
Andrew McNamara
andrewm@connect.com.au
connect.com.au Pty. Ltd.
Level 3, 213 Miller St
North Sydney, NSW, Australia
Adopted and adapted by:
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA