Directly in Thunderbird
Go to Edit > Account Settings
- Type / Edit your signature directly in the Window.
If the input area is locked, please uncheck the "Attach a signature from a file instead"
Press OK
Signature in a File
You can still use your .signature file:
Check the box Attach the signature from a file instead
- Go to the file-location.
In this case: /home/c/nem/.signature
Edit the file with your favorite Texteditor. F.e. nedit