Rated 5 out of 5 stars

Από τον/την Vlad στις Σεπτ. 26, 2011 · μόνιμος σύνδεσμος

Great add-on - 5 stars! To me, it should be a default Thunderbird feature.
If you plan to improve, I would vote for two things:
1. Ability to mark composed message for follow-up, directly from compose window. (Without going to Sent folder right after sending it).
2. Back-link from the event/task to e-mail(s) for follow-up.
Again, very well done and THANKS!