Thunderbird - LQWiki

From LQWiki

Thunderbird is a free, open-source and cross-platform email client for most operating systems including, Windows, Linux and Macintosh. It is based on the Mozilla codebase. It is a robust and easy to use client, similar to competing products like Outlook Express, Evolution, but with some major advantages such as junk mail classification.

Unlike Mozilla, which is a complete suite of web related applications, such as a browser, a mail/news client, a chat client and much more, Thunderbird is just a mail client.

Being just a mail client has its advantages, it is a better choice if you already have a browser like Firefox or Galeon for example.