As this bug was not present in Ubuntu 9.10 Karmic Koala (thunderbird 2.0.0.24+build1+nobinonly-0ubuntu0.9.10.3), it must have been introduced sometime in between karmic and lucid.
As this bug was not present in Ubuntu 9.10 Karmic Koala (thunderbird 2.0.0.24+ build1+ nobinonly- 0ubuntu0. 9.10.3) , it must have been introduced sometime in between karmic and lucid.