How to add html email signature in Apple Mail?
Note: The steps mentioned here are w.r.t. macOS Monterey version 12.5. If this doesn't work for you, please get in touch with Apple support for the steps to add an HTML email signature w.r.t. your OS.
Go to QRCodeChimp's Email Signature popup, select the desired email signature template and click on 'Copy Embed Code.'
Log into your Apple Mail app and click on 'Mail,' then on 'Preferences,' and then on the 'Signatures' tab.
You'll see all your connected email accounts in the left column.
Select the account to which you want to add the signature. Then, click on the '+' icon to create a new signature.
Name the signature, remove the default signature text and uncheck the 'Always match my default font' checkbox.
Close the Preferences window to save it, and then quit the Mail app.
In Finder, select the menu bar item 'Go' and click on 'Go to Folder.'
Copy/paste this signature folder path: ~/Library/Mail/V6/MailData/Signatures/ in the popup and click on 'Go.'
A list of file names will appear.
Locate the most recently modified file that ends with '.mailsignature,' right-click on it, select 'Open with' and choose 'TextEdit.'
Select the code from the line starting with <body> to the end of the file and replace it with the copied embed code (refer step 1 to copy embed code).
Save and close the file, then quit TextEdit.
To test that it works correctly, compose a new email using the account you associated with this new signature. If the images show, and everything looks as it should, you have succeeded!