Claws Mail

Claws Mail is a free and open-source, C/GTK-based e-mail client, which is both lightweight and highly configurable. Claws Mail runs on both Windows and Unix-like systems such as Linux, BSD, and Solaris. It stores mail in the MH mailbox format. Plugins allow to read HTML mail, but there is none to compose HTML messages.

Features
Claws Mail is also a news client and RSS aggregator. Further features – integrated or supplied via plugins – include:


 * Search and filtering, optionally via Perl and Python scripting
 * Security (GPG, SSL, anti-phishing)
 * Anti-spam (SpamAssassin, Bogofilter)
 * Per-folder preferences
 * Optional external editor
 * Templates for messages
 * Themes support, customisable toolbars, X-Face support, foldable quotes
 * Viewers for HTML mail (Dillo, Gtkhtml2, Fancy (WebKit), LiteHTML)
 * TNEF attachment parser
 * PDF viewer
 * Various notification plugins, e. g. trayicon and LED handler
 * Archiving, import/export from standard formats
 * Support for Mbox mailbox format
 * Calendaring with events as kind of messages

History
Development started in April 2001 as Sylpheed-Claws off the development version of Sylpheed, where new features could be tested and debugged. In August 2005 Claws Mail forked completely from Sylpheed.