Announced yesterday (Sept 14, 2016) on their Google Apps Developer Blog says that Gmail will soon be able to handle CSS media queries.
Later this month, you’ll be able to use CSS media queries with Gmail and Inbox by Gmail to ensure that your message is formatted the way you intended, whether it’s viewed on a computer, a phone in portrait mode, or a tablet in landscape mode. You’ll be able to change styles based on width, rotation, and resolution, allowing for more responsive formatting to optimize your email for every device.
In my mind this has rather large implications, because like web standards, as a designer and developer I’d love it if one day the language of the web is language of email too. I know inline CSS works, but imagine one day just being able to copy over your CSS base styles and use that in your email blasts.
I look forward to seeing how, if at all, this is handled by locally based email clients.