Quick answer
Set a Thunderbird signature for the intended account or identity, then test it in a new message. An external signature file must remain accessible on that computer.
Applies to
For an existing mailbox you are authorized to use in Thunderbird. For Interactive Online hosted mail, copy the exact secure settings from Email Accounts > Connect Devices. Account Hub and older Account Settings setup flows differ by Thunderbird version.
Steps
- Open Account Settings and choose the intended account or identity.
- Enter signature text, use supported HTML, or select a signature file. Check that images and contact details are appropriate for recipients.
- Compose a new message and review the signature for that From identity before sending.
Check the result
Send a controlled test and inspect the received result, including any linked images and reply behavior.
Troubleshooting and support
If the signature is absent, check the selected identity, new/reply signature preferences and any moved external file.
If the problem continues, contact support from the account that owns the service. Include the domain, exact error, time and time zone, tool name, and a redacted screenshot. Keep passwords, private keys, cookies and private message content out of the ticket.
Video tutorial
The original video is preserved. Its interface or product version may differ from the written guidance above.
Related help
Official references
Written content reviewed November 1, 2026. Menu availability depends on the product version, permissions and service.
