What guidelines for HTML email design are there? [closed]

Answer 1

Always use multipart mime and provide a plain text alternative.

Answer 2

The folks behind Campaign Monitor also started a Email Standards Project web site with a lot of good information.

Answer 3

Three words of advice: test, test, test.

Check out LitmusApp.com's email testing service. You send them a message and they render it in a bunch of clients and show you screenshots of the results. It's not perfect, but it's pretty good.

(Lotus Notes prior to 8.0 really, really stinks for HTML mail, by the way)

Also, beyond just inline CSS styles, I recommend switching to tags wherever possible.