Dovecot

Dovecot is an IMAP server for Linux/UNIX-like systems, written with security
primarily in mind. It also contains a small POP3 server. It supports mail
in either of maildir or mbox formats.

Lets install it:

[root@vm01-lin-01 ~]# yum -y install dovecot

And start the service:

[root@vm01-lin-01 ~]# /etc/init.d/dovecot start
Starting Dovecot Imap: [ OK ]

Cool. All set.