Microsoft has made a somewhat controversial change to their Outlook 2007 mail client which will utilize an internal HTML rendering engine rather than that of Internet Explorer. While this makes for a more stable email client, it does cause some issues.
The most visible effect is that more complex HTML pages will not look right when viewed in Outlook. It seems an odd move to make an upgrade with less functionality, but there is some security gained from it. An Explorer bug cannot be exploited through an email now, but is it worth the loss of functionality? My thought is no. The answer should be to do a better job of protecting Explorer, not make a change that reduces email functionality.
A simple fix would have been to put decent HTML/CSS rendering code into Outlook. The poor job their current code does must have been because it was rushed out the door. Most people will probably be disappointed to get an updated email client only to find that it doesn’t work as well.