Highly recommended Rated 5 out of 5 stars
As a consequence of doing business I have accumulated well over 6000 email messages located in 500 folders and sub-folders (up to five levels deep). I am really happy with QuickFolders for easing access to my messages. I actually sent Axel $50USD. If my business ever recovers I will try to do something similar for other extension developers. Money is the best rating system there is.
I've been sending email since about 1985 and using Thunderbird since 2001. It's the best IMO.
I also recommend Allow HTML Temp, CompactHeader, Copy Sent to Current, Folderpane Tools, Manually sort folders, Printing Tools, Quicktext, and Show Address Only.