Claws Mail is an open source software project that has been designed from the ground up to act as a lightweight email client application suitable for Linux-based operating systems that use a lightweight window manager/desktop environment. It is was previously known as Sylpheed-Claws.
Features at a glance
Key features include support for multiple accounts, support for GnuPG, colored labels, MIME attachments, threaded display, user-defined headers, email filtering, support for reading and posting Usenet new, as well as support for SSL connections for the IMAP4, POP3, SMTP and NNTP protocols.
In addition, it comes with a user-friendly, sophisticated and modern graphical user interface written in GTK+ and compatible with the GNOME, MATE, Cinnamon, LXDE or Xfce desktop environments, quick response, easy configuration, stability, intuitive operation, robustness and a powerful plugin architecture that lets users to extend its core functionality.
Under the hood and availability
A quick look under the hood will tell us that the application is written entirely in the C programming language, except for the graphical user interface, of course, which is written with the help of the GTK+ GUI toolkit. It is available for download as a source archive and can be installed on both 32-bit and 64-bit platforms.
However, the best way to install Claws Mail in your GNU/Linux operating system is to use the officially supported or community-derived packages provided in the main software repositories. Keep in mind though, that if your Linux distro has no packages for Claws Mail, you can still configure, compile and install the source archive.
Summing up, Claws Mail is indeed a very fast, stable, reliable and user-friendly email client that can rival even the powerful Mozilla Thunderbird applications. You can find it installed by default in a wide range of lightweight GNU/Linux operating systems. Before you can use the email client, it is a must to configure a default email account.