Rated 4 out of 5 stars

Great add-on. Only one problem which makes me give it a 4-star rating:

It seems like the threading algorithm doesn't take messages from other folders into account. For example, in my inbox I have a lot of replies to emails I've sent out, and the visualization puts a grey square where my outgoing emails should be. The outgoing emails are in my "sent" folder but I guess ThreadVis doesn't see/consider that.

This review is for a previous version of the add-on (1.1.595).