Should email be 99.9% typography, too?

No, email should be plain text.

Please, get some contrast.

Indeed, I stopped reading.

If the web is 99.9% typography, then this article is 99.9% unreadable. I see this 'gray text on white' mostly from designers/developers using Macs. Is it something in the guideliness or is it because of Apple's website design that so many of them emulate it? Or does it look so good on Retina displays that it is foisted upon all others?

http://contrastrebellion.com/

It's often due to OS X's font rendering resulting the text being much heavier than on Windows, but in this case it looks pretty much the same between Windows, non-retina OS X and retina OS X,