DirigoDev - 4:08 pm on Jul 3, 2013 (gmt 0)
Mailchimp has several RWD templates published on Git. You'll also find other RWD email templates in Git. The net-net is that RWD email templates don't work yet. You'll need to settle on a 320px wide template for the time being. If you're dead-set on RWD you're going to spend a ton of time trying to make it work. I blew 100+ hours before I gave up.
I have a client who uses Constant Contact. They have a 600px wide footer that cannot be changed. So, if you're using CC, forget about anything less than 600px wide. As an FYI - for a few hundred $$ CC will build you a smaller footer (I'm not a fan of CC). In general, all of the ESPs are behind the curve on mobile friendly email. It is so very sad. Let's hope the industry responds to our needs.