Claws Mail is a secure, lightweight mail client as well as a news reader that is based on GTK+, making the customization aspect an especially noteworthy advantage. Designed to be user-friendly, quick as well as stable, it also features additional functions such as a: RSS aggregator, calendar, and laptop LED handling, as well as numerous others that can all be downloaded via extra plugins. For users looking for something that is simplistic that offers a multi-lingual experience as well as the ability to customize multiple accounts, then this may be the mail client for them.
To provide a little history, Claws Mail was originally a fork of Sylpheed and was, at the time, called Sylpheed Claws. It added exciting new features to the original program and fed them back into the original project as much as possible. Eventually, Sylpheed and Sylpheed Claws diverged into to two separate entities and are not completely different programs, with Claws Mail continuing to evolve from its original features.
Native to Linux distributions and platforms initially, Claws Mail also offers a Windows port with its most current update at version 3.8. The newest version, no matter what format you get it in, works as a fantastic and simplistic setup with customization options that far exceed the often stringent rules of Outlook. Along with its easy accessibility, this simplistic mail client also does a fantastic job of handling return addresses when configured with multiple accounts by automatically using the address that the email was initially sent to.
While it offers no email integration via Outlook or Thunderbird, workarounds with various plugins have been found that help negate this issue. Claws Mail itself imports and exports in mbox email formats, which are not found outside of Linux typically. Again, there are workarounds for this via the ImportExportTools add-on for Thunderbird. If exporting from Outlook, users will have to export to Thunderbird first and then use the add-on. The process is worth it for the full customization and fluidity of a fully configured Claws Mail client, however.
From its native Linux, this light-weight and flexible mail client has continue to grow as a competitor to other mail clients such as Thunderbird and Outlook. It continues to see more updates, features and extensions, and is sure to keep improving as time goes on. For those looking for a good alternative, Claws Mail is most definitely worth giving a chance.