FossaMail is a Thunderbird-based mail, news and chat client from the developers of the Pale Moon browser.

The program features Pale Moon-like compiler optimizations "geared towards an as stable and smooth operation of the client as possible", and also uses the Pale Moon browser core as its back end.

FossaMail looks and feels just like Thunderbird, and it should run all Thunderbird (v24/25b era) add-ons and plugins.

FossaMail stores its data in a custom location (%APPDATA%\FossaMail), allowing you to install and run FossaMail and Thunderbird on the same system.

There's also an optional calendar, Lightning, available from the developer's site.

What's new in v38? (changelog)

- This version bumps the application version to 38.0 for reasons of add-on compatibility.
- The only other change is no longer directly relying on for extension updates


FossaMail is a straightforward email client with plenty of worthwhile features. We're unsure if it's significantly better than Thunderbird, but you can install and run the programs together, so it's easy enough to compare the two.