I just wanted to give you an update about the release of Outlook 2010.
An acid test by Litmus compares 2007 vs 2010 and to be honest their is really no diffrence in rendering the email.
What should email designers be doing differently for Outlook 2010 vs 2007? To be honest, nothing. As always: Keep your email simple, use tables for layout, inline your CSS and follow the other email design guidelines for Outlook 2007.
Kenny Van Beeck