Seems that Microsoft will hit hard in email design after they said that the new Outlook 2007 will stop using the Internet Explorer engine to render the email content and will use instead Microsoft Word rendering engine. The reason of doing this is because of security they said.
Using the new render engine means poor css support like: no background images, background color will fail, almost no float or position properties (this will kill all css based design, we will have to use tables), almost no support for padding and margin.