Rated 5 out of 5 stars

Great add-on. I use it from a long time.
For making this add-on work with Thunderbird 3.0.1 you should do:
- Delete this add-on
- download add-on to your harddrive
- Open xpi-file with WinRar (or other)
- open file install.rdf
- change the text 3.0a1
to 3.0.1
- save the file
- start Thunderbird and import xpi-file.