Hi there.

I'm running into some issues whilst trying to test Gmail's CSS rendering, using <style> tags in the <head>.

I've seen a successful test - just delivering to myself for speed, and viewing on Gmail web - which suggest to me that it is reading and rendering the CSS.

However, if I add in my mobile styles, then none of the styles are read - both mobile and desktop rendering is broken.

I've tried experimenting by only including a handful of mobile styles, and whilst the results seem to be quite hit and miss, I certainly have seen successful rendering of the email on desktop when I've also included a mobile-specific media query.

That led me to wondering whether there's a limit, either by bytes, lines, selectors or attributes, as to how much CSS you can include in the head? At the moment, when I try to include my mobile styles, it appears as though none are rendered at all.