Will Thunderbird 5 appear in the official 11.04 repositories?
Solution 1:
Mozilla is still supporting Thunderbird 3.1.x, so that's what's currently shipping in 11.04 so it will remain that way until it has been end-of-lifed by the Thunderbird team.
(I suspect it won't take them long to follow Firefox and at that point you'll receive both the latest Firefox and Thunderbird on every Ubuntu release at the same time but it's not quite there yet, though that is the final goal).
In the meantime for users that want it, they can snag the latest Thunderbird from a PPA:
- How do I install the latest stable version of Thunderbird?