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How to add an HTML signature in Thunderbird

Thunderbird can use HTML typed into the signature box or an HTML file. Both methods, how to include a logo and what plain-text readers see.
The Sendoff team2 min read

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Open Account Settings, select your email address, and paste your HTML into the Signature text box with Use HTML ticked. Or tick Attach the signature from a file instead and choose an .html file. For a logo, reference an image hosted at a public HTTPS address in the HTML. Recipients who read mail as plain text see only the text, without images.

Method 1: paste HTML

  1. Open the menu (three lines) > Account Settings.
  2. Click your email address in the left column.
  3. Tick Use HTML (e.g., bold) under Signature text.
  4. Paste your signature HTML into the box.
  5. Close the tab. Settings save automatically.

Method 2: use a file

  1. Save your signature as an .html file. One way, from Mozilla's guide: write an HTML message with your signature, use File > Save As and choose the HTML type, then discard the message.
  2. In Account Settings, tick Attach the signature from a file instead (text, HTML, or image).
  3. Click Choose and pick the file.

The file method is handy when the HTML is long or several accounts share one signature.

Logos and images

  • Link images from a public HTTPS URL. A local file path works on your computer but breaks for recipients.
  • Set width and height on the <img> tag so the logo does not appear huge in other clients.
  • Make sure you compose in HTML. If an account is set to compose in plain text, Thunderbird sends a text-only signature.

Make the HTML

Sendoff's HTML signature generator builds table-based HTML with inline styles that Thunderbird, Gmail and Outlook all render. Copy the HTML source and paste it into the signature box. See also the Thunderbird install guide.

FAQ

Why does my Thunderbird signature show HTML code? The Use HTML box is not ticked, so Thunderbird treats the code as text.

Can each Thunderbird account have its own signature? Yes. The signature is set per account, and each identity can have its own.

Why do recipients not see my logo? The image points to a local file or the recipient reads plain text. Use a hosted image.

Sources

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