A quick not to let you know that Google as announced a few days ago that gmail will support media queries, and no longer CSS inlining within a month. See Official Gmail Blog: Better emails, tailored to all your devices
This is great news for email template developers, since, it will make it much easier to create responsive email on android devices (note: may templates are not fully responsive for the moment on android devices. They just zoom out, but keep a desktop layout). See here to see a real example of the difference between zoom-oout and real responsive: Google Apps Developer Blog: Your emails, optimized for every screen with responsive design
This will also work for Inbox.
Last point, gmail is still not the standard email client on Android 4.4, but it is on Android 5. If any one could share here recent stats of the market shares of the various versions of android, that would be great.
Hopefully, it will also put the last vendors that do not support media queries (namely MSFT) to move in that direction or be completely cornered...
They have done more for developers productivity and reduction of headache painkillers in one day than in years