Review for TB Header Tools Extension by sven
Rated 4 out of 5 stars
Great program, but as said before, you may lose the attachments of IMAP messages. To prevent this view the message's source code (Ctrl-U) before changing the header. This should force TB to download the complete message.
To avoid any risk, also activate the "Put Original message in Trash folder".
To create your own collections, you must have a Mozilla Add-ons account.