Thunderbird has red borders inside and around the signature
updated 15 days ago
You've just added a new signature in Thunderbird, and when you send a new message, it has a bunch of red lines around the layout of the signature like on a screenshot below?
That's okay! Thunderbird uses these red borders to show you where there are HTML tables and cells. However, those are not part of the HTML and should not appear in the sent/received message.
Just send your new message, and your receivers won't see these lines.
If you still looking for a way to delete these dotted red borders, you can turn them off by doing the following:
Open the Thunderbird Menu and click Options.
Scroll down to Config Editor.
You get a warning to be careful. Just click "I accept the risk".
Double click on "mail.identity.default.suppress_signature_separator" to change its value to true.
Close the config window and compose a new email.