I was a "template engineer" for emails as one of my first Jobs the problem is the range of clients that's why still to this day tables are the most stable solution that are displayed everywhere correctly.
Outlook to my knowledge uses the word rendering engine for HTML, I will leave out lotus notes where everything below ~ 2px will be displayed as 16px (y ? ask IBM) ....
So basically I would say .... f*ck it use a table layout and it will be stable enough .... just make the design a classic scroll-able thing and don't use CSS3 if it should look every where the same, if they don't care about consistency just don't use HTML5
I've done it only for 2 years and maybe my knowledge is outdated but I know that we got a lot of money just to make them look everywhere the same.
j
stuff ;)