Mozilla made public the first beta of Thunderbird 3.1 today. Code-named Lanikai and available for Windows, Mac, and Linux, the milestone makes few noticeable changes to the open-source and free desktop e-mail client. This is not surprising, though, as Mozilla Messaging announced that the goal of this release was to fix problems created by upgrading the Gecko engine that powers the program.
Lanikai is the first semi-stable release of Thunderbird to use Gecko 1.9.2, which is the same engine that Firefox 3.6 uses. The changes made from Thunderbird 3 to the 3.1 beta test version include Mac OS X 10.6 upgrade path from Thunderbird 2 improvements, fixes for autocomplete, tabs, activity manager, minor interface improvements and corrections, and a spate of stability and memory corrections.
One new security feature is that Lanikai requires extensions to come from a secure server using the HTTPS protocol or be digitally signed. Absent either of these, the extension won't install.
The full list of bug fixes is available here.
There are also several known issues that persist in Lanikai. These include a conflict with the Kaspersky Anti-Spam add-on, an occasional plain-text e-mail interface bug that forces buttons out of the pane, and an occasional offline bug that prevents e-mails written in Offline mode from being automatically sent when the Internet connection is restored. They must instead be sent manually from the Drafts folder.
As noted when Lanikai entered the alpha phase of development, Mozilla Messaging is attempting to follow in the footstep of the Firefox release schedule. The final version of Thunderbird 3.1 is expected sometime in June, though that could easily change.