FossaMail is an Open Source mail, chat and news client for Windows and Linux, based upon the Mozilla Thunderbird client. The application is an alternative version of the Mozilla client and the user interface and the speed of Fossamail appear almost the same as Mozilla's Thunderbird.
Key Features Include:
FossaMail uses the Pale Moon browser core as its back-end.
FossaMail uses its own profile folder on your system, so it will not interfere with any existing Thunderbird client installations you may have.
FossaMail is compatible with all Thunderbird (v24/25b era) add-ons and plugins.
FossaMail includes optional calendar/organizer add-ons.
System requirements: Windows Vista or above (Windows XP is not supported), a processor with SSE2 support. The application is available for both Windows and Linux.