How to Add an Email Signature in Thunderbird

Thunderbird needs the signature as HTML source code, not a plain copy-paste, plus one checkbox turned on first.

Updated August 2026

  1. Build your signature with the Mail Ink editor, save it, and click Copy source code (not "Copy to clipboard") on the install screen.
  2. Open Thunderbird and click the menu button in the top right corner.
  3. Go to Preferences > Account Settings.
  4. In the Signature text section, check Use HTML.
  5. Paste the signature code (Ctrl+V or Cmd+V).
  6. Save changes. Done!

Frequently asked questions

You need to check "Use HTML" in Account Settings > Signature text before pasting - without it, Thunderbird strips all formatting and treats the signature as plain text.

Yes - signatures are set per-account. Open Account Settings, select the account in the left sidebar, and set its signature separately from your other accounts.

Use "Copy source code" for Thunderbird. Its signature field expects raw HTML once "Use HTML" is checked, not a rich-text paste the way Gmail or Outlook accept.

Copy-pasted images can end up embedded as attachments instead of linked online, which some providers block. Signatures built in the Mail Ink editor use hosted image links, so this isn't an issue as long as you paste the exported source code.

Yes, by default - Thunderbird doesn't have a separate new-email vs. reply/forward toggle like Gmail does. Remove it manually on a message if you don't want it there.

Setting up another email client?

Gmail
Outlook
Apple Mail
iPhone & iPad

Don't have a signature yet?

Build one free in the Mail Ink editor, then come back and follow the steps above.

Create your free signature