Sylpheed - lightweight and user-friendly e-mail client -http://sylpheed.sraoss.jp/
Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA).
Sylpheed runs on Unix-like systems such as Linux, BSD, and Mac OS X. It also supports Windows.
Sylpheed uses GTK+ GUI toolkit. The newest version of Sylpheed works with GTK+ 2.4 or later (2.6 or later is recommended).
Sylpheed is a free software distributed under the GNU GPL (the library part is GNU LGPL). You can freely use, modify and redistribute it under the license.