Tame Your Email With Thunderbird
The Elusive and Confusing Signature Attachment
It’s no secret that Thunderbird has a less than desirable signature file system, but until a better one is implemented, the idea is to make due with what you have.
I would recommend setting up a folder in your Thunderbird profile directory called ‘thunderbird-sigs’ and create a new text document for each email account.
This makes attaching, updating, and keeping track of all your signature files a snap.