Here is a quick guide on how to upgrade Thunderbird 2 that comes with Ubuntu 9.10 Karmic Koala to glorious Thunderbird 3. Hopefully this will save some lost souls out there. :)
Open Terminal and copy folder ~/.mozilla-thunderbird to the new location expected by Thunderbird 3:
copy ~/.mozilla-thunderbird ~/.thunderbird
All emails, settings and extensions in ~/.mozilla-thunderbird will be [...]
