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.

We will be shutting down FossaMail in May.

Since there hasn't been any positive response to the request for new maintainership for this (mostly charity-run) project, we'll be shutting down FossaMail.

No further official releases will be made, we'll shut down the website and support forum (@ Pale Moon), and everyone currently using FossaMail should be looking for a replacement mail/chat/news client within the next few months to avoid running into potential security vulnerabilities as time goes on.

Thank you all for your years of support!

  • 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/Goanna 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 many Thunderbird add-ons and plugins of the same version.
  • Is available in 32-bit (x86) and 64-bit (x64) versions for both Windows and Linux.
  • Comes with an optional calendar/organizer integrated that will allow it to be used in a Microsoft Outlook style information manager fashion.
System requirements:
  • Operating system either:
    • Windows Vista or above, 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: 38.2.0

Release notes for FossaMail can be read here.

The program (32-bit or 64-bit) is available from our file mirror:

Download from file mirror

Other downloads:
You may find other downloads for specific platforms available that are allowed in accordance with the FossaMail redistribution license for officially-branded binaries (either our builds or exempted rebuilds for specific platforms and OS distributions) on other sites. Please read this license carefully if you are planning to redistribute FossaMail to remain in compliance for publishing and distributing officially-branded binaries.


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:
Site and contents © 2014-2017 Moonchild Productions - All rights reserved
FossaMail is released as Open Source under the Mozilla Public License (MPL) 2.0
FossaMail in binary/executable form is subject to its Redistribution License
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