For over a year I have been designing and coding all of my email campaigns to be 580 pixels wide. They are responsive so on mobile everything shifts to a different layout. Lately I have been seeing several branded emails come into my inbox much wider than what I'm creating. Question is, has the standard width for emails finally gone up? Is it safe to design at ~650 or even ~700 (or higher?).
As everything I'm doing is responsive, it seems like it shouldn't matter what my upper width is (barring increased image and k-size of course).
What is the current industry standard? What issues would I run into by going greater than 580 pixels.
Bonus question: I notice that if I resize the window for Apple Mail or Thunderbird, the emails that I send respond to the window change. This does NOT happen w/ Gmail. Any reason why? Sure would be great if it would respond like the others. How/when does Gmail decide what version of the email to display?