NAME

       regexp_table - format of Postfix regular expression tables

SYNOPSIS

       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, mail routing, or
       access control. 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  compared  against  a  list of patterns. When a match is found, the
       corresponding result is returned and the search is terminated.

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

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

COMPATIBILITY

       With  Postfix version 2.2 and earlier specify "postmap -fq" to query a table that contains
       case sensitive patterns. Patterns are case insensitive by default.

TABLE FORMAT

       The general form of a Postfix regular expression table is:

       /pattern/flags result
              When pattern matches the input string, use the corresponding 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.

              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 logical line.

       Each pattern is a POSIX regular expression enclosed by a pair of delimiters.  The  regular
       expression syntax is documented 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 non-alphanumerical  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,  and  newlines  are  not  treated  as  special
       characters.  The  behavior  is  controlled 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.

       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.

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

TABLE SEARCH ORDER

       Patterns are applied in the order as specified in the table, 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  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.

TEXT SUBSTITUTION

       Substitution of substrings (text that matches  patterns  inside  "()")  from  the  matched
       expression  into the result string is requested with $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.
       /[%!@].*[%!@]/       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
       if !/^owner-/
       /^(.*)-outgoing@(.*)$/   550 Use ${1}@${2} instead
       endif

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

       postmap(1), Postfix lookup table manager
       pcre_table(5), format of PCRE tables
       cidr_table(5), format of CIDR tables

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview

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

                                                                                  REGEXP_TABLE(5)