Claws Mail is a free and open-source, C/GTK-based e-mail client, which is both lightweight and highly configurable.

[2][3] Claws Mail runs on both Windows[4] and Unix-like systems such as Linux, BSD, and Solaris.

[5] Claws Mail is also a news client and RSS aggregator.

Further features – integrated or supplied via plugins – include:[6][7] 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.