I've started rethinking my approach to HTML e-mails in light of the impact of mobile devices (that new iPhone 4S I got for Christmas definitely helped). I've started some research and experimentation using inline CSS to design e-mails that work both on desktop clients and mobile.
Has anyone else started in this direction? There are some challenges (Outlook 2007 anyone?), but it does seem do-able if you're willing to simplify your layout. I'd love to hear about other peoples experience or thoughts.