Hey there! It's not impossible that Muse could generate HTML for email, but I can see a few potential and major problems. Basically, Muse will be generating code for a web environment, but Emma will only accept code for an email environment. Emma also has some additional requirements for code. If Muse could generate code that would fall within all of those guidelines for both Emma and email in general, it would work, but it doesn't look like this is the purpose of Muse.
More specifically, HTML in email is extremely limited when compared to HTML used on the web. While Muse is a program designed to make the advanced features of HTML easy to create and publish, email HTML requires a simpler approach that will render properly in a wide variety of environments, some that are nearly 10 years old (I'm looking at you, Outlook 2007). If you could use Muse to create HTML that falls within our guidelines outlined here, it would work. If it won't fall within those guidelines, it probably won't save within Emma. Even if it could, there would still be the larger problem of correct rendering in all of the inboxes you would send to.
I hope this clears things up! Please let me know if you have any more questions!