Review for Signature Switch by Hisky
Rated 5 out of 5 stars
Just testing around but right now it works fine with 91.4.1!
I can send email and receive them without any issues. (right now i just use a html signature without JPGs etc.)
I love the idea of the autodetection by URL of the sender of the email. (in case you reply)
To create your own collections, you must have a Mozilla Add-ons account.