HOW-TO: Upgrade to SquirrelMail 1.4.3a on cPanel
"SquirrelMail is a standards-based webmail package written in PHP4. It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages render in pure HTML 4.0 (with no JavaScript required) for maximum compatibility across browsers. It has very few requirements and is very easy to configure and install. SquirrelMail has all the functionality you would want from an email client, including strong MIME support, address books, and folder manipulation."
"cPanel includes SquirrelMail 1.4.0 which was released back on the 3rd April, 2003, which is now over a year old! This HOW-TO takes you through installing the latest version of SquirrelMail, which at the time of writing is version 1.4.3a, plus guides you in how you can further customise your installation with many of the plug-ins currently available."
http://unofficial-support.com/node/view/49