I saw a weird bug with buttons in Office 365 and Outlook.com where instead of normal looking bulletproof button, somehow the colored border wound up wrapped around the next <td> in my code, and the button lost any padding/shape and the text even changed to black (it was white). Needless to say it was a strange bug - why was it applying the border of the button to the next <td> element?

But after some tinkering I figured out the reason was that I was using a placeholder link of href="#" and Office 365/Outlook.com seem not to like that. Changing it to href="http://someurl.com/ fixed the problem.

Just wanted to share this incase anyone came across this issue. Using href="#" for a link placeholder might cause weird button behavior when previewing Office 365/Outlook.com.