Review for Thunderbird Conversations by Flozo
Rated 4 out of 5 stars
This addon is the main reason I'm still using Thunderbird. It works very well and after ajusting some settings I get exactly what I want: a clean interface with a well organized conversation-view.
It would become even better if one could drag entire conversations (containing mails from different folders i.e. in- and outbox) to a another folder.
To create your own collections, you must have a Mozilla Add-ons account.