Thunder Sign Editor

Rated 5 out of 5 stars

by Benno Yorck on Sept. 7, 2026 · permalink

A super handy plugin. I had been looking for a way to edit formatted signatures directly in Thunderbird—similar to how it's done in Outlook—for a long time.

For anyone wondering how to use it after installation:
In Thunderbird's standard view (i.e., when no settings window is open), you will find a new "Thunder Sign Editor" button in the top right corner, next to the Minimize, Maximize, and Close buttons. This button is only visible when you are in Thunderbird's email view.

A couple of suggestions for improvement:
- You cannot resize Base64-encoded images after pasting them (e.g., from Word). To do this, you have to manually adjust the HTML/CSS via Thunderbird's standard signature settings.
- It would be great if the "Thunder Sign Editor" modified the standard signature input window directly, placing the plugin's functionality where it logically belongs: right within Thunderbird's account settings input area.