Rated 5 out of 5 stars
Thought it conflicted with Thunderbird Conversations, but re-enabling it after an upgrade to TBird 12.0a has it working. Some sort of temporary glitch?
If you're using Thunderbird 11.0 or higher, you'll need to download the latest beta of Conversations. The Conversations dev and I have coordinated on things so that nothing will break, provided you're on the right versions.