Rated 5 out of 5 stars

David P wrote:
"However, the Add-on overrides the standard Thunderbird behavior when REPLYING -- where Thunderbird beautifully chooses the identity, based on one's own mail address that the original mail was SENT to."

Well in MY case TB did exactly the opposite and was sending mail with the wrong address when I did not pay attention to choose the correct account whereas the Seamonkey mail client did it correct. But as I use some addons that have no equivalent in SeaMonkey I was very pleased with this add-on. In my case I always route mail to certain folders, connected to a certain account and in the past replying to lists always picked the right mail address as "sent" but that behaviour suddenly disappeared and it took me a lot of effort to first find out why and changing settings in the about:config.
So: Big thank you for creating and maintaining this add-on!

This review is for a previous version of the add-on (6.0).