Long time ago I wanted to run a complete mail server for my company. I decided to encrypt and authenticate connections for both sending and receiving mail, and to handle receiving mail with IMAP, rather than POP. The final setup can handle large amounts of both incoming and outgoing mail and is easy to use. This tutorial is about Debian Wheezy plus a group of reliable applications that will give us a good and trustful mail server.
Read the complete tutorial in https://doc.axrglobal.com/servidores:mail:mail_system_debian_wheezy