We are having a similar problem. We are on 15.7 and every email sent within our domain (from one staff person to another) comes through as text, including emails with HTML that we forward to each other. When we click on VIEW, the VIEW HTML option is not there.
Also, for other incoming email, it is frustrating to have to pick VIEW HTML for every single email. Can't SmarterMail know the difference, and can't we set up a preference?