[sensanaty]

Way I interpret it is that that you write down your markup/CSS, and the app spits out compliant HTML that will render properly regardless of email client.

Might be wrong, though.

[hunter2_]

Sounds like a bit like Emogrifier [0] or other "inliners" but media queries seem a bit suspect.

[0] https://www.myintervals.com/emogrifier.php