Mozilla announced Miramar Alpha 1, an early version of their next Thunderbird.
Miramar Alpha 1, available here for download, is for testers, extension developers, and other friends who are curious to follow the development of the next release of Thunderbird.
Miramar Alpha 1 is built on top of the next generation of Mozilla’s layout engine, Gecko 2.0 and includes a new Addon Manager and over 190 platform fixes to improve performance and stability. We expect to release further interim releases as we work towards a major new release of Thunderbird.
Please read the release notes for more details.