Not a big surprise that Apple Mail, iOS Mail, and Thunderbird are the winners here. They're the clients most likely to allow HTML through verbatim in most cases.<p>Sadly, at least in my case, most people are using Gmail on the Web and they filter the HTML in numerous mystifying ways (although this is ultimately good for us as users IMHO).<p>Luckily there's still a <i>lot</i> that most mass e-mailers can do, including myself, to make e-mail pleasant for readers without niceties like custom fonts.. but one day it would be great to universally expect something a little more elaborate than HTML 3.2 ;-)