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REGEXP_TABLE(5)                                                REGEXP_TABLE(5)

NAME
       regexp_table - format of Postfix regular expression tables

SYNOPSIS
       postmap -fq "string" regexp:/etc/postfix/filename

       postmap -fq - 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. In this case, each input is com-
       pared against a list of patterns,  and  when  a  match  is
       found the corresponding result is returned.

       To  find out what types of lookup tables your Postfix sys-
       tem supports use the "postconf -m" command.

       To test lookup tables, use the "postmap  -fq"  command  as
       described in the SYNOPSIS above.

TABLE FORMAT
       The general form of a Postfix regular expression table is:

       /pattern/flags result
              When pattern matches the input string, use the cor-
              responding result value.

       !/pattern/flags result
              When  pattern  does not match the input string, use
              the corresponding result value.

       if /pattern/flags

       endif  Match the input string against the patterns between
              if and endif, if and only if that same input string
              also matches pattern. The if..endif can nest.

              Note: do not prepend whitespace to patterns  inside
              if..endif.

              This feature is available in Postfix 2.1 and later.

       if !/pattern/flags

       endif  Match the input string against the patterns between
              if and endif, if and only if that same input string
              does not match pattern.  The  if..endif  can  nest.
              matches pattern. The if..endif can nest.

              Note:  do not prepend whitespace to patterns inside
              if..endif.

              This feature is available in Postfix 2.1 and later.

       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.

       Each  pattern  is a POSIX regular expression enclosed by a
       pair of delimiters. The regular expression syntax is docu-
       mented  in  re_format(7)  with  4.4BSD,  in  regex(5) with
       Solaris, and in regex(7) with Linux. Other systems may use
       other document names.

       The  expression  delimiter  can  be  any character, except
       whitespace or characters that have special meaning (tradi-
       tionally  the  forward slash is used). The regular expres-
       sion can contain whitespace.

       By default, matching is case-insensitive, and newlines are
       not  treated  as  special characters. The behavior is con-
       trolled by flags, which are toggled by  appending  one  or
       more of the following characters after the pattern:

       i (default: on)
              Toggles  the  case  sensitivity  flag.  By default,
              matching is case insensitive.

       x (default: on)
              Toggles the extended  expression  syntax  flag.  By
              default,  support for extended expression syntax is
              enabled.

       m (default: off)
              Toggle the multi-line mode flag. When this flag  is
              on,  the  ^  and $ metacharacters match immediately
              after and immediately before a  newline  character,
              respectively,  in addition to matching at the start
              and end of the input string.

TABLE SEARCH ORDER
       Patterns are applied in the order as specified in the  ta-
       ble,  until  a  pattern  is  found  that matches the input
       string.

       Each pattern  is  applied  to  the  entire  input  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 [email protected]  mail  addresses  are  not
       broken  up  into  their user and domain constituent parts,
       nor is user+foo broken up into user and foo.

TEXT SUBSTITUTION
       Substitution of substrings  from  the  matched  expression
       into  the  result  string  is possible using $1, $2, etc.;
       specify $$ to produce a $ character as output.  The macros
       in  the  result  string  may need to be written as ${n} or
       $(n) if they aren't followed by whitespace.

       Note: since negated patterns (those preceded by !)  return
       a result when the expression does not match, substitutions
       are not available for negated patterns.

EXAMPLE SMTPD ACCESS MAP
       # Disallow sender-specified routing. This is a must if you relay mail
       # for other domains.
       /[%[email protected]].*[%[email protected]]/       550 Sender-specified routing rejected

       # Postmaster is OK, that way they can talk to us about how to fix
       # their problem.
       /^[email protected]/       OK

       # Protect your outgoing majordomo exploders
       if !/^owner-/
       /^(.*)[email protected](.*)$/   550 Use ${1}@${2} instead
       endif

EXAMPLE HEADER FILTER MAP
       # These were once common in junk mail.
       /^Subject: make money fast/     REJECT
       /^To: [email protected]\.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
       postmap(1), Postfix lookup table manager
       pcre_table(5), format of PCRE tables
       cidr_table(5), format of CIDR tables

README FILES
       DATABASE_README, Postfix lookup table overview

AUTHOR(S)
       The regexp table lookup code was originally written by:
       LaMont Jones
       [email protected]

       That code was based on the PCRE dictionary contributed by:
       Andrew McNamara
       [email protected]
       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

                                                               REGEXP_TABLE(5)