Comment 101 for bug 239360

Thank you for taking the time to report this bug and helping to make Ubuntu better. This bug has been reported to the developers of the software. You can track it and make comments here: https://bugzilla.mozilla.org/show_bug.cgi?id=387480

According to this bug report, a fix has already been made. Unfortunately, this fix will not be available prior to Thunderbird 3, which is still in development, except by installing the extension as you have noted. Since this is a workaround, and the bug is not fixed in a released version, I will mark this bug as Confirmed.