DOKK / manpages / debian 12 / postfix / regexp_table.5.en
REGEXP_TABLE(5) File Formats Manual REGEXP_TABLE(5)

regexp_table - format of Postfix regular expression tables

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


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. Use "postmap -hmq - <file" for header_checks(5) patterns, and "postmap -bmq - <file" for body_checks(5) (Postfix 2.6 and later).



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.










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 the input string matches /pattern/, then match that input string
      against the patterns between if and endif. 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 the input string does not match /pattern/, then match that input
      string against the patterns between if and endif. 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.

  

  

  
Empty lines and whitespace-only lines are ignored, as are lines whose
      first non-whitespace character is a `#'.

  

  
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:



  

  
Toggles the case sensitivity flag. By default, matching is case
      insensitive.

  

  
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.

  

  
Toggles the extended expression syntax flag. By default, support for
      extended expression syntax is enabled.












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.










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.










The contents of a table may be specified in the table name
    (Postfix 3.7 and later). The basic syntax is:




main.cf:


    parameter = .. regexp:{ { rule-1 }, { rule-2 } .. } ..
master.cf:


    .. -o { parameter = .. regexp:{ { rule-1 }, { rule-2 } .. } .. } ..


Postfix ignores whitespace after '{' and before '}', and writes
    each rule as one text line to an in-memory file:




in-memory file:


    rule-1


    rule-2


    ..


Postfix parses the result as if it is a file in /etc/postfix.


Note: if a rule contains $, specify $$ to keep
    Postfix from trying to do $name expansion as it evaluates a parameter
    value.








# 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








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








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








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










Use "postconf readme_directory" or
    "postconf html_directory" to locate this information.


DATABASE_README, Postfix lookup table overview








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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA