With the Thunderbird 5 Beta release, we’ve enabled the 5.* maximum version in the AMO Developer tools. Thunderbird 5 Beta is now API frozen, so if you haven’t already done so, please make sure your add-on is compatible. We expect it to be released near the end of the month.

For add-ons, the most significant change in Thunderbird 5 is the new Add-on Manager that was incorporated into Firefox 4. There is documentation and further information on developer.mozilla.org.

If you have any further questions or concerns, please post in the forums, or join #extdev on irc.mozilla.org for real-time assistance.

We’re working on the Thunderbird 3 release, currently on beta 2. To support the release, we are working on improving our documentation for writing Thunderbird add-ons. Thunderbird developers will notice that there has been some housecleaning and some new material over on the Thunderbird extension area of the Mozilla Developer Center.

You can help! You can be a beta tester. Or you can dive into writing Thunderbird add-ons. Or you can help us with the documentation project. We’re particularly looking for people to write “how-tos”: short blurbs that contain code snippets illustrating how to do things with Thunderbird extensions. There are some topic ideas here.

If you’re new to the Thunderbird email client, you can download the latest stable version here. Thunderbird add-ons are available here.