From Oxxus Wiki
As part of services handled within Linux OS, the e-mail services stands for one of the most utilized after web related ones.
Every Linux OS related distro comes with email services packages. All of them are SMTP agents, which stand for Small Message Transfer Protocol, and provide required engines for email services basic functioning.
Commonly used ones are Postfix, Exim and SendMail. All of them can work out of a box but in order to have emails handled correctly each of them requires additional configuration.
While SMTP is authoritative for exchanging email messages between servers, for accessing email inboxes certain services are required as well. There are two protocols that are in use, POP3 and IMAP.
Main difference is that POP3 retrieves messages from server to client side while IMAP leaves messages on server. One of most used service is Dovecot that handles both protocols correctly, although there are others like POPa3D etc..
Please see links below on how to install, configure, analyze and familiarize with the interface.