Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind. Dovecot is an excellent choice for both small and large installations. It's fast, simple to set up, requires no special administration and it uses very little memory.
- dovecot basic dovecot, exim and fetchmail. A basic setup where dovecot hosts the mail, exim is the MTA, and fetchmail is used to grab external mail using POP3.