Outlook 2013 Pro for Windows 8 is showing all HTML messages in mobile format.  They look fine in any web based client, but on the desktop client, it's the mobile view.  I've tried resetting views and toggling CSS, but nothing helps it.  It's incredibly strange, any suggestions?

Hi,

Would you please provide a screenshot regarding the mobile format so that we can understand it more clearly? If your account is not verified to upload an image in the forum, you can share the screenshot to us by sending it to GBSD TN Office Information Collection  ibsofc@microsoft.com.

Regards,

Steve Fan
TechNet Community Support

Here's an example, though this is from another support request post I found that had no answer, I'm seeing exactly the same things with a variety of HTML emails.