Comment 25 for bug 261595

Are you using Thunderbird 2 from the Ubuntu repositories? This issue is not fixed in Thunderbird 2, nor is it likely to become fixed. This is only solved in the Thunderbird 3 beta since beta 4pre.

If you would like to try using the Thunderbird 3 betas, please go to https://edge.launchpad.net/~ubuntu-mozilla-daily/+archive/ppa and follow the directions there for adding that PPA to your repository list. Then install the thunderbird-3.0 package to get Thunderbird 3. Please keep in mind that this is beta software, so you should make sure to have a full backup of any relevant data (in this case, your ~/.mozilla-thunderbird/ folder) before you start using this.