how to insert html signature in [your program here]
Instructions below were taken from: htmlsignature.com/how-to-create-and-install-a-html-email-signature-in-google-gmail
CTRL-C) to your clipboard.
CTRL-V) the email signature design you have stored in the clipboard.
Mail.app is a little trickier but, not hard once you understand how to do it. The links below show you using their sample files, just use the one generated from this form instead.