I'm a graphic designer. I design emails in html. I hate doing them because they all render differently in different email clients. gmail, outlook, apple mail.
Even MailChimp will cock up my sliced up PNG by adding extra lines of HTML/CSS.
But businesses can't sell stuff with plain text emails (IMHO). That's not the reality of business and retaining subscribers. So what's the safer alternative to HTML but allows for graphics and call-to-actions?