Xmodulo posted a tutorial abouts how to set up a working mail server in Ubuntu or Debian

This tutorial will discuss how to set up a working mail server in Ubuntu or Debian. As we know, the two major protocols used in a mail server are SMTP and POP/IMAP. In this tutorial, postfix will be used for SMTP, while dovecot will be used for POP/IMAP. Both are open source, stable and highly customizable.

Please note that securing a mail server is beyond the scope of this tutorial, and will be covered in future tutorials.

  How to set up a mail server in Ubuntu or Debian