Great stuff from some folks who know an awful lot about email:
If there’s a medium that lends itself to progressive enhancement, it’s email. Given the contexts in which email content is parsed and displayed (and will be in the future), it pays to consider content first and independently from the presentation.
Traditionally, email designers have taken all sorts of scrappy approaches to ensuring that text in email “looks the same across all clients”. Your Gmail experience should be the same as your Outlook experience and so-forth. I’d argue that “reading the same across all clients” is vastly more important and that when possible, visually lovely flourishes should be added, for the environments that support them.