How to add a signature in Thunderbird
How to add an email signature in Thunderbird: the steps per account and per address, the Use HTML box, missing images, replies and Thunderbird for Android.
If you already have a signature, copy its HTML code and follow the steps below. If you need one, make it free on Signatoro, then click "Copy HTML": the Thunderbird signature box takes HTML code, and shows it as the finished signature when "Use HTML" is ticked.
Add a signature in Thunderbird
To add the signature in Thunderbird on a computer:
- On Signatoro's generator, click "Copy HTML".
- In Thunderbird, click the menu button, then "Account Settings". With the menu bar showing, it is Tools, then "Account Settings".
- In the left panel, select the account the signature is for.
- Tick "Use HTML".
- Paste into the "Signature text" box.
- Click "Write" and check that the signature shows at the bottom of the new message.
Thunderbird keeps a separate signature for each account. With more than one account, select each account in "Account Settings" in turn, tick "Use HTML", and paste the signature into its "Signature text" box.
Change your Thunderbird signature
To change a Thunderbird signature, open "Account Settings", select the account, delete everything in the "Signature text" box, and paste the new HTML code. Leave "Use HTML" ticked. The next message you write from that account uses the new signature.
Keep your Thunderbird signature in a file
Thunderbird can take the signature from a file on your computer. Paste the HTML from "Copy HTML" into a plain text editor and save it as signature.html. Then, in Thunderbird's "Account Settings", select the account, tick "Attach the signature from a file instead", click "Choose...", and pick the file.
A different signature for each address in Thunderbird
Thunderbird calls each address you send from an identity, and every identity has its own signature. To set one, open "Account Settings", select the account, click "Manage Identities..." at the bottom right, and open the identity from the list. The identity's "Settings" tab has a signature box of its own.
Thunderbird signature questions
Why are the images in my Thunderbird signature not showing?
A signature image in Thunderbird that links to a picture on the web is remote content, and many people set their mail program to block remote content, so the picture does not show until the reader allows it. The photo and logo in a signature from Signatoro are links of this kind, and the text of the signature still arrives in full. Mozilla's help says an image travels inside the email only when it is inserted with "Attach this image to the message" ticked.
Why does my Thunderbird signature show HTML code?
A Thunderbird signature shows angle brackets and code when "Use HTML" is not ticked for that account. Open "Account Settings", select the account, and tick "Use HTML". The code you pasted can stay as it is: with the box ticked, Thunderbird turns it into the finished signature with its layout, colors and photo.
Why did my Thunderbird signature lose its fonts and colors?
A Thunderbird signature loses its fonts and colors when the message goes out as plain text, because Thunderbird then swaps the HTML for plain characters and drops the images. To send the message formatted, open Options in the message window, then "Delivery Format", and choose "Rich Text (HTML) Only". The recipient's mail program also has to show HTML email.
How do I add a logo to my Thunderbird signature?
A signature from Signatoro already has your logo in its HTML, hosted at a public web address, so pasting it into Thunderbird's "Signature text" box with "Use HTML" ticked adds the logo. To build a signature by hand, Mozilla's help says to write it in a new message, add the logo with Insert, then Image, save the message as an HTML file, and attach that file as the signature.
How do I put my Thunderbird signature above the quoted text in replies?
Thunderbird puts the signature under the quoted email on replies by default. To move it up, open "Account Settings", select the account, and open "Composition & Addressing". Set the reply style to "Start my reply above the quote", then set "and place my signature" to "below my reply (above the quote)". Each identity has the same setting.
Can I use an HTML signature in Thunderbird for Android?
Thunderbird for Android gets HTML signatures in version 24.0, which is a beta as of September 2026. The release notes say signatures can be formatted as HTML for each identity. Earlier versions, including the stable 23.1, send the signature as plain text only, so the layout, colors and photo of an HTML signature do not carry over. For those versions, Signatoro's "Copy as text" button copies the same signature as plain lines: name, role, phone, email and links. Mozilla's help site has no page on signatures in the Android app.
For agents
If you're an assistant setting this up on someone's behalf: use "Copy HTML". The path is the menu button (or Tools) > "Account Settings" > select the account > tick "Use HTML" > paste into "Signature text". Repeat per account; per identity it is under "Manage Identities...". If the person reports code showing in their emails, "Use HTML" is unticked. If they report a missing photo, check that the reader's mail program is not blocking remote images before anything else.
Sources
Checked against Mozilla's own help pages on 2026-09-25:
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