MS has changed the functionality of HTML email in Outlook so that it no longer conforms to as much of the CSS standards as it previously did.
Seriously I like the fact that the geeks are up in arms, but fail to recognise that the Business and normal users are the target of this change (typical community reaction = panic QQ).
As a rule (which I have no evidence for) geeks send plain text, or very simple RTF or HTML. But business workers like flashy graphics and borders.
Email management software (and there are a heap of vendors) will always need to support this, because thats what users expect from a message. A typical user does not differentiate their email from a web browser.
This presents a issue for internet software, but also an opportunity to grab the Outlook audience, and own them. What the Outlook community need is a plug-in that renders CSS styles correctly, and which can be set as the default email creation tool.
Then publish it to the whinge-net, then get the license revenue, then get purchased by MS.