PLEASE NOTE: This add-on is currently maintained by @mikehardy and others at https://github.com/mikehardy/thunderlink
Current versions from that repository appear to have fixed all known regressions that accumulated over time as thunderbird was updated, and work well with all major operating systems, so the add-on works as it did when it was first created.
Please use that repository to report feature requests or issues, or submit pull requests.
Thanks!