REGEXP_TABLE(5)

NAME
regexp_table - format of Postfix regular expression tables

SYNOPSIS
regexp:/etc/postfix/filename
postmap -q "string" regexp:/etc/postfix/filename
postmap -q - regexp:/etc/postfix/filename <inputfile

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. To test lookup tables, use the postmap command as described in the SYNOPSIS above. The general form of a Postfix regular expression table is:

/pattern/flags result

!/pattern/flags result
    When pattern matches (does not match) a search string, use the corresponding result value.

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.

if /pattern/flags

if !/pattern/flags

endif
    Examine the lines between if..endif only if pattern matches (does not match). The if..endif can nest. Do not prepend whitespace to patterns inside if..endif.

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, that is, treat newline characters as special). Each pattern is applied to the entire lookup key string. 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 substrings from the matched expression into the result string is possible using $1, $2, etc.. The macros in the result string may need to be written as ${n} or $(n) if they aren't followed by whitespace.

EXAMPLE SMTPD ACCESS MAP
# 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

EXAMPLE HEADER FILTER MAP
# These were once common in junk mail.
/^Subject: make money fast/     REJECT
/^To: friend@public\.com/       REJECT

EXAMPLE BODY FILTER MAP
# First skip over base 64 encoded text to save CPU cycles.
~^[[:alnum:]+/]{60,}$~          OK
# Put your own body patterns here.

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