Sylpheed is an e-mail client (and news reader) based on GTK+, running on
X Window System, and aiming for
* Quick response
* Simple, graceful, and well-polished interface
* Easy configuration
* Intuitive operation
* Abundant features
The appearance and interface are similar to some popular e-mail clients for
Windows, such as Outlook Express, Becky!, and Datula. The interface is also
designed to emulate the mailers on Emacsen, and almost all commands are
accessible with the keyboard.

The messages are managed by MH format, and you'll be able to use it together
with another mailer based on MH format (like Mew). You can also utilize
fetchmail or/and procmail, and external programs on receiving (like inc or
imget).