Firefox 2 and Gecko 1.8 End of Life
vm writes "According to Mozilla and other sources, Firefox 2 and Gecko 1.8 will soon be left behind some time in mid-December. The end result: no future security or stability updates. This will affect Thunderbird 2, SeaMonkey 1.1, Camino 1.5, and any other projects based on Gecko 1.8. So, if you haven't already upgraded, there's no time like the present."
Thunderbird 3 is under development. An alpha version is available.
Even so, it is poor practice to end support for one of your products when its successor hasn't even been released yet.