Sylpheed is an email client and newsreader based on the GTK+.
It offers quick response, easy configuration and an abundance of features, like scoring and filtering. Sylpheed is free software licensed under the GPL.
Sylpheeds classic branch focuses on stability. It is maintained by Sylpheeds founder Hiroyuki Yamamoto.
The experimental Sylpheed-claws branch offers extra features on the bleeding edge, like plugins for SpamAssassin and anti-virus software. The branches resync regularly.
Documentation for Sylpheed is worked on in an additional multilingual project.
Sylpheed's official homepage
Sylpheed documentation project