Mozilla this week made available the first beta of Thunderbird 3 for Windows, Mac, and Linux. Codenamed "Lanikai," the latest release introduces a few changes to the open-source email client, many of which take place under the hood.

Built on top of the Gecko 1.9.2 platform (the same engine powering Firefox 3.6), Mozilla says you can expect improvements in stability and memory, fixes to improve upgrading from Thunderbird 2, fixes for auto complete, tabs, and activity manager, and several design improvements and corrections to the interface.

As with any beta software, you should expect a few bugs, and there are a handful of known issues in Thunderbird 3. Kaspersky's Anti-Spam extension is disabled, for instance, and you may run into some SMTP issues.

If you still want to give it a try, you can download a copy right here.

Release Notes
Changelog

Mozilla earlier this week released its Thunderbird 3 email client in stable form, which introduced a handful of new features, like tabbed email and a new search interface. It also contains code from an unlikely source - the French military.

It all started six years ago when the French military chose Mozilla's open-source software rather than roll with Microsoft's proprietary software. The reason? The open-source nature allowed the military to tinker with the code and build security extensions.

"We started with a military project, but quickly generalized it," said Lieutenant-Colonel Frederic Suel of the Ministry of Defense and one of those in charge of the project.

Some of the work the French military did on Thunderbird ended up being released to the public under the name "TrustedBird," of which Thunderbird 3 borrows some of the code.

"The primary changes (the military" have made allow them to know for sure when messages have been read, which is critical in a command-and-control organization," said David Ascher, chief executive of Mozilla Messaging.