This is an example email's <head> code (just the Page Source grabbed from a preview of the browser version-Firefox 50.0.2-of the email) that could probably have better standard resets, client-specific resets, mobile styles and client-specific mobile styles, (and in-line HTML, but that is not included). I would greatly appreciate any critiquing of this CSS so that such an email will render better when opened in the top 10 email clients (we all know them)
Sorry, I'm not an email CSS expert so I can't really critique this for you, but if you want to test how well your email renders across the top email clients have you tried Hubspot's "Test in different email clients" feature in the email editor?