Mozilla has announced the release of a second alpha for version 3.3 of Thunderbird, code named "Miramar". Like Firefox 4, which is also currently in development, the early version of Mozilla's next generation open source email client is based on version 2.0 of the Gecko rendering platform – the Thunderbird 3.1 and Firefox 3.6 branch use Gecko 1.9.2 – and features a new Add-ons Manager and extension management API.

Aimed at "testers, extension developers, and friends who are curious to follow the development of our next release of Thunderbird", the second alpha features the addition of a new Troubleshooting information page (about:support) to help users diagnose and fix problems. The developers also note that the attachment reminder now works again and that attachment sizes are now available in the compose window.



Thunderbird 3.3 Alpha 2 on Mac OS X. Other changes include updates to the add-on installation progress notifications and platform fixes for nearly 100 bugs found in the previous alpha version. Thunderbird 3.3 will include several user interface improvements for Windows 7 and Vista, as well as support for 32 and 64-bit Mac OS X systems – however, it will no longer support PowerPC (PPC).

As with all development releases, use in production environments and on mission critical systems is not advised. Installing Miramar Alpha 2 may overwrite existing installations of Thunderbird on Linux systems – Thunderbird will install to different locations on Windows and Mac OS X. Users testing the release are encouraged to provide feedback and report any bugs that they encounter.

Further information about the development preview, including a list of known issues, can be found in the release notes. Thunderbird 3.3 Alpha 2 is available to download for Windows, Mac OS X and Linux in English (US) only. The developers note that future Beta and Release Candidate versions will be made available in more languages.

Thunderbird binaries are released under the Mozilla Thunderbird End-User Software License Agreement and the source code is released under disjunctive tri-licensing that includes the Mozilla Public Licence, GPLv2 and LGPLv2.1. The latest stable release is Thunderbird 3.1.7 from the 9th of December, a security and maintenance update that addressed several critical vulnerabilities.

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