Virtual Users And Domains With Postfix, Courier And MySQL (CentOS 5.1)

Version 1.0
Author: Falko Timme <ft [at] falkotimme [dot] com>
Last edited 12/05/2007

This tutorial is Copyright (c) 2007 by Falko Timme. It is derived from a tutorial from Christoph Haas which you can find at You are free to use this tutorial under the Creative Commons license 2.5 or any later version.

This document describes how to install a Postfix mail server that is based on virtual users and domains, i.e. users and domains that are in a MySQL database. I’ll also demonstrate the installation and configuration of Courier (Courier-POP3, Courier-IMAP), so that Courier can authenticate against the same MySQL database Postfix uses.

The resulting Postfix server is capable of SMTP-AUTH and TLS and quota (quota is not built into Postfix by default, I’ll show how to patch your Postfix appropriately). Passwords are stored in encrypted form in the database (most documents I found were dealing with plain text passwords which is a security risk). In addition to that, this tutorial covers the installation of Amavisd, SpamAssassin and ClamAV so that emails will be scanned for spam and viruses.

The advantage of such a “virtual” setup (virtual users and domains in a MySQL database) is that it is far more performant than a setup that is based on “real” system users. With this virtual setup your mail server can handle thousands of domains and users. Besides, it is easier to administrate because you only have to deal with the MySQL database when you add new users/domains or edit existing ones. No more postmap commands to create db files, no more reloading of Postfix, etc. For the administration of the MySQL database you can use web based tools like phpMyAdmin which will also be installed in this howto. The third advantage is that users have an email address as user name (instead of a user name + an email address) which is easier to understand and keep in mind.

This tutorial is based on CentOS 5.1 (i386). You should already have set up a basic CentOS system, as described here: and Plus, you should make sure that the firewall is off (at least for now) and that SELinux is disabled (this is important!), as shown in the chapter six on

This howto is meant as a practical guide; it does not cover the theoretical backgrounds. They are treated in a lot of other documents in the web.



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