From my experience with emails, none of the clients read divs
very well. You're better off using tables
to get the layouts of your emails.
When doing emails you need to stick the the SIMPLEST HTML you can, inline styles, etc.
Gmail is quite good when it comes to compatibility, unless it's imported fonts, it doesn't like fonts!
For your email layout, I'd split it into 2 rows.
Your first row would be an image, the whole width of the email, containing the top, say, 100px
of that layout.
Under this, have your content with borders on the left, right, bottom, and style="padding-left: Ypx"
Y being the distance between the left border and the start of the text.
(Yes, padding does work in HTML emails, but not if they're responsive.)
I can give you more if you want, just let me know.