Signatures are defined for each account, so if you create an html signature for account A, save it as sigA.html, make changes for account B, save as sigB.html, ... repeat for other accounts. (The file can a .txt file if it is just plain text.) Set the signature for each account in Account Settings. If you have multiple signatures for each account, they can be managed with add-ons like Quicktext or Signature Switch.

Sfhowes, I understand and agree with with all you've posted. And that's what I've done in my accounts. I've also created signature files that reference images files.

I'll explain further what I hope to do. As you know, in Account Settings and just below the 'Signature Text:' box, there is the setting: 'Attach the signature from a file instead (text, HTML, or image):' One could reference the same file from multiple accounts. Since you can use HTML in the Signature file, is there some HTML code that could retrieve the Thunderbird's account email address or other Thunderbird info?

Sfhowes, I understand and agree with with all you've posted. And that's what I've done in my accounts. I've also created signature files that reference images files. I'll explain further what I hope to do. As you know, in Account Settings and just below the 'Signature Text:' box, there is the setting: 'Attach the signature from a file instead (text, HTML, or image):' One could reference the same file from multiple accounts. Since you can use HTML in the Signature file, is there some HTML code that could retrieve the Thunderbird's account email address or other Thunderbird info?

You need a html file for each account because you do not want to use the same sig file as it does not contain the necessary email address in the signature. In Folder Pane, Select the account name which is using correct signature - click on Write It has a signature displayed. Edit the signature so it has Account 2 email address and save as html file eg: sig2 Then in Account 2 attach that sig2 html file. REpeat for other accounts.