Rated 4 out of 5 stars

This extension works very well, but I dislike the default of plain text signing. It's a great way to annoy everyone on a mailing list... It seems the rationale is to have better support for receivers using bad mail clients, but I doubt they're verifying emails via copy-paste if they can't be bothered to use another client.

This review is for a previous version of the add-on (1.6).