Domain aliasing

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Purpose

Sometimes you may come across a situation when you should provide email services to a "domain", which is more like an alias for another domain. Typical example is: 

domain.com <-> mail.domain.com .

All the users who can be reached via user@domain.com should also be reached via user@mail.domain.com

Life with Qmail-LDAP (http://www.lifewithqmail.org/ldap/#domain%20aliassing) describes a method for domain aliasing through control/virtualdomains and default forward rules. It has only one major disadvantage: you cannot use RCPTCHECK with alias domains as those are treated as non-locals. This drawback can result in a great number of unsolicited bounces.

Usage

This patch introduces a new config file: control/aliasdomains
This file is a colon-separated list of 

alias_domain:real_domain

mappings. All LDAP queries on mail address are modified so that alias_domain is replaced by real_domain.

It doesn't matter if aliasdomains file is non-existant or empty. If no match is found for the domain part of the queried mail address, it is queried unmodified.

Notes

  • alias_domain must be listed in both control/rcpthosts and control/locals but need not be in control/virtualdomains or in LDAP mail addresses
  • an alias_domain must point to a real_domain (so no multiple redirection applies)
  • once you have switched on domain aliasing, if you have an LDAP entry that has only "alias_domain" mail addresses, it wouldn't be found.
  • of course, you can have many alias_domains mapping to the same real_domain

Download & Install

You have to add -DDOMAIN_ALIAS to LDAPFLAGS in Makefile.

Test

You can check this functionality with qmail-ldaplookup: 

# cat /var/qmail/control/aliasdomains
mail.iif.hu:iif.hu
# /var/qmail/bin/qmail-ldaplookup -m devnull@mail.iif.hu
Searching ldap for: (&(objectClass=qmailuser)(|(mail=devnull@iif.hu)(mailAlternateAddress=devnull@iif.hu)))
Note the difference between iif.hu and mail.iif.hu!

If properly set up, bad recipient addresses can be rejected SMTP time by using RCPTCHECK.

--Bajnokk 18:32, 7 March 2007 (CET)

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