Let’s take a step to the bad old days of HTML 3. Since people don’t keep their email clients as up to date as their browsers, compatibility with even basic CSS 2 on email clients is around where it was in 2001. As a result, table based layout still rules the day here. I don’t like it either.
Gmail App has had, for some time, a severe bug that is demonstrated and explained in this HTML file. In summary, if you build an image based html email you can expect gmail to crack it up, literally. I tried for three days - though I found the cause, I could not find a fix. Even if there is one (which at this point I doubt) Google should correct this problem.
Oh, and a fun bit of irony - this problem is linked to a zoom bug that affects Firefox, Chrome and Safari. The only browser that doesn’t have this problem? Internet Explorer. In fact, IE has never had this problem from the point zoom was first added to it in version 7.