So you want to add a signature at the bottom of every right? No problem! First, open a text editor, for Mac that would be TextEdit, for Windows that would be NotePad. First, make sure the document is plain text – in TextEdit, go to Format > Make Plain Text; you’re already set up for this in NotePad.
In this new, plain-text document, make your signature. You can have whatever you want in this signature, including HTML for links, etc. When you finish making your signature, save it somewhere convenient and with a name that’s easy to remember; mine is emailsig.txt.
Next, open Thunderbird and go to Tools > Account Settings. Click on the name of the account that you want to add the signature to and check the box next to “Attach this signature”. There is a box below that checkbox where you put the path to the file you just made in TextEdit/Notepad. The easiest way to do that is to use the Choose button and go hunt for it. So click on the Choose button at the far right end of that blank box and it will open a mini-Finder/Explorer window. Find the signature file you made earlier and click OK. That fills in the path for you.
You should be good to go. You can test drive your new signature by opening a new email. Your signature should be at the bottom. If it doesn’t look the way you wanted it to look, open the text file you made earlier and edit it. You are able to edit the signature at the bottom of the email, of course, but it will be wrong on every email if you don’t fix it in the text file.
Posted by Slushman 