Running your own email server with Mail-in-a-Box
How to install and maintain your own mail server using Mail-in-a-Box on Ubuntu 14.04.
Setting up a Postfix Mail Server with Dovecot
Postifx is a very popular mail server that can be setup on Linux relatively easily and it is extremely configurable and easy to maintain. Paired with Dovecot for POP/IMAP functionality, you can have a basic mail server setup within minutes.