MySQL users, Postfix, Dovecot & SquirrelMail with userprefs stored in mySQL

Name: MySQL
HomePage: http://www.mysql.com/
function: MySQL, the most popular Open Source SQL database

Name: Dovecot
HomePage: http://dovecot.org/
function: Dovecot is an open source IMAP and POP3 server for Linux/UNIX-like systems, written with security primarily in mind.

Name: Squirrel Mail
Homepage: http://www.squirrelmail.org/
function: Webmail client, used to check e-mails from anywhere in world, via the internet, like gmail or hotmail

Name: Postfix
HomePage: http://www.postfix.org/
Function: (message transfer agent) postfix is program responsible for receiving incoming e-mails and delivering the messages to individual users

Name: PostfixAdmin
HomePage:  http://high5.net/postfixadmin/
Function: Postfix Admin is a Web Based Management tool created for Postfix. It is a PHP based application that handles Postfix Style Virtual Domains and Users that are stored in MySQL.

backups with Bacula, MySql & Apache

Name: Apache
HomePage: http://www.apache.org/
function: Webserver

Name: MySQL
HomePage: http://www.mysql.com/
function: MySQL, the most popular Open Source SQL database