Prevent Gmail Cleansing of Attached HTML

I have created a single HTML file th开发者_运维知识库at includes its own CSS styling, as well as custom HEAD tags so that it displays in a mobile browser fairly nicely. I then have it working with PHP as a file attachment.

Trouble is this -- Gmail is munging the View of it, but not the Download of it. Gmail is stripping out the CSS and rebuilding the HEAD without my custom viewport stuff.

Is there a programmatic way to code the HTML5 to cause Gmail to fail in doing this cleansing?

My only advice (and it sucks because it means a lot more work) is to put the styles inline with the html as much as you can. That seems to get past at least some of their filtering.