It was a little ridiculous how difficult it was to figure this out but after a bunch of searches here’s the best thing.
- Design an HTML signature in some HTML editor. Save that file as “Signature.html”.
- Open “Signature.html” in a text editor. Copy the HTML to the clipboard
- In “Mail” open “Preferences -> Signatures”
- Create a simple signature by pressing the “+” button
- Quit Mail App.
- Open “Safari” and navigate to this URL:
file:///Users/<USER NAME>/Library/Mail/V2/MailData/Signature NOTE: Replace “USER NAME” with your user
- Your “Finder” should have opened automatically. Put it into “List” view and sort by “Date Modified”. You should see a file that looks like a long, random set of letters and numbers that ends with “.mailsignature”. Right click that file and select “Open With” and use your TextEdit program.
- Copy the HTML code from your signature to this file. Replace everything except the final
<br class=”Apple-interchange-newline”> as that is a carriage return that you want to keep for cleanliness.
- Open Mail back up. Start a new email. If you don’t have a signature you should see a drop-down menu with the choice for your new signature. Select it and Voila! HTML fancy good ness.