Note: These instructions only apply to Landau identifiers!
A single signature in Thunderbird can be set as follows:
1. Navigate to the account settings. (First click on the bar symbol, then move the mouse to "Settings", wait briefly, then click on Account settings)
2. set the desired text in the account settings (1) under "Signature text" (2).
Attention: With these settings, only one signature can be created per account. If there is a need for multiple signatures in an account, an ad-on such as "Signature Switch" is required.