Rated 5 out of 5 stars

To make it work with Thunderbird 2.x you will need to make a slight tweak as described below:

1. Change the extension from .xpi to .zip and open the file.
2. Edit the file install.rdf with a text editor and change the maxVersion from 1.6 to 2.1.
3. Save the file replacing the original in the archive.
4. Install the add-on as normal.