Welcome to the FossaMail homepage!

FossaMail is an Open Source, Mozilla Thunderbird-based mail, news and chat client for Windows and Linux, brought to you by the Pale Moon developers (and therefore not affiliated with the Mozilla Corporation). It is an alternative version of the Mozilla Thunderbird mail&news client, and based on the Pale Moon browser core.

  • Is built from source with compiler optimizations geared towards an as stable and smooth operation of the client as possible (Pale Moon-alike optimizations).
  • Uses the Pale Moon browser core as its back-end. The client is therefore based on Pale Moon rather than other Mozilla-derived mail clients.
  • Uses its own profile folder on your system. This means it will not interfere with existing Thunderbird installations.
    The default profile location is %APPDATA%\FossaMail
  • Should be compatible with all Thunderbird (v24/25b era) add-ons and plugins.
  • Is available in 32-bit (x86) and 64-bit (x64) versions for both Windows and Linux.
  • Comes with an optional calendar/organizer add-on (Lightning, available from the download location below) that will allow it to be used in a Microsoft Outlook style information manager fashion.
System requirements:
  • Operating system either:
    • Windows Vista or above (Windows XP is not supported), OR
    • A recent Linux distribution (it will not run on particularly old kernel/libc combinations)
  • A processor with SSE2 support
  • Sufficient hard drive space to install and store your e-mail and other data
  • An internet connection ;-)

Current version: 25.2.0

Both the program (32-bit and 64-bit) and the lightning add-on are available from FOSSHub:

Download from FOSSHub


Support for FossaMail is provided by the Pale Moon community. You can discuss bugs, give feedback and ask for support on the Pale Moon forum. You may also want to check out the Mozilla help pages for Thunderbird for general use questions, considering its functionality and feature set being extremely similar.

Source code:
The source code is available on GitHub:
Thunderbird, Mozilla Thunderbird and Mozilla are registered trademarks of the Mozilla Corporation.
Site and contents © 2014-2015 Moonchild Productions - All rights reserved
FossaMail is released under the Mozilla Public License (MPL) 2.0
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