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Apple Mail · macOS

How to add an HTML email signature in Apple Mail

Disclaimer: This method requires editing system files. Always back up your data first. BlueDevLabs Ltd accepts no liability for issues arising from following these steps. See our full terms and conditions.
Why is this more involved? Apple Mail does not have a direct HTML paste option. We need to replace the signature file on disk directly.

Step-by-step installation

  1. Create a placeholder signature in Apple Mail

    Go to Mail → Settings → Signatures. Select your account, click +, type "REPLACEME". Close Mail completely (Cmd+Q).

  2. Find your signature file

    Open Finder, press Cmd+Shift+G, navigate to: ~/Library/Mail/V10/MailData/Signatures/. Find the most recent .mailsignature file.

  3. Open it in TextEdit

    Right-click the file and open with TextEdit. You will see header lines and your "REPLACEME" placeholder.

  4. Replace the body with your SigForge HTML

    Keep the header lines at the top and replace everything after the blank line with your SigForge HTML code.

  5. Lock the file

    In Finder, right-click the file, click Get Info, and tick Locked. This stops Mail overwriting it.

  6. Re-open Mail

    Open Apple Mail and compose a new email to see your signature.

Tip: If the signature shows as blank, quit Mail completely, make sure the file is locked, then reopen.

Other email clients

Gmail setup guide Outlook setup guide