Android Issue Display Block (Responsive)

Hello Enrique. You're right : without a doctype, the WebKit rendering engine behaves differently. And among the differences we can see, display:block doesn't work. You can read more about this issue at Email on Acid. Please note that this issue isn't specific to Android. Any client using WebKit removing doctypes will behave that way. The Yahoo app on iOS for example is also concerned.

Mike Ragan recently suggested to use <th> tags instead of <td>s to get around this problem. In case that wouldn't work for you, I really invite you to try another approach like table stacking or creating a responsive email without media queries.

I hope this helps. Feel free to ask if you have any other problem.