I've been struggling with mobile resizing for my emails, particularly with font size. I've read some other topics in this forum, tried media queries, but still can't override this resizing thing. Any tips or tutorials I can take a look?
Are you including the CSS in the head?
Try this template that I wrote as a starting point, changing the CSS to suit your brand. This seems to work well for me across devices/screen sizes, although for note, it doesn't appear to fit in the mobile preview.
Get it on PasteBin with the password sendy
Hope it helps,