squirrelmail 2:1.4.20-1ubuntu0.1 (amd64 binary) in ubuntu lucid

 SquirrelMail is a standards-based webmail package written in PHP. It
 includes built-in pure PHP support for the IMAP and SMTP protocols, and
 is designed for maximum compatibility across browsers. SquirrelMail has
 few requirements and is easy to configure and install. It runs on top of
 any IMAP server.
 .
 SquirrelMail has all the functionality you would want from an email client,
 including strong MIME support, address books and folder manipulation.