Web browsing and e-mailing from Mozilla got a bit of a bump forward on Wednesday, as the company updated its beta test builds of Firefox 3.6.4 and Thunderbird 3.1, respectively code-named Lorentz and Lanikai.

Firefox 3.6.4 beta 3, for Windows, Mac, and Linux, and Thunderbird 3.1 beta 2, for Windows, Mac, and Linux, offer the latest features from Mozilla but are also less stable than the current releases.

When pushed out to all users, Firefox 3.6.4 will incorporate the much-anticipated Out-Of-Process-Plug-in feature, which prevents plug-in crashes from Adobe Systems' Flash, Apple's QuickTime, and Microsoft's Silverlight from bringing down the entire browser. You can read the change log here, but the gist of it is that Firefox 3.6.4 beta 3 continues to fix bugs related to OOPPs (out-of-process plug-ins), including about a dozen marked critical.

According to Mozilla's calendar, Firefox 3.6.4 is still on track to be released in the second week of May.

Thunderbird 3.1 beta 2 introduces multiple fixes as well. The new build continues to improve the migration process from Thunderbird 2, which many users complained was buggy and problematic. It also tweaks the auto-complete feature, tab usage, and the activity manager that debuted in Thunderbird 3.

Along with stability and memory leakage improvements, the beta version makes some minor changes to interface, such as improving the default font selection, when available. The full change log for Thunderbird 3.1 beta 2 can be read here.

This Thunderbird beta build was released on time. If the schedule holds, users can expect a release candidate for Thunderbird 3.1 two weeks from now, with a final version by the beginning of June.