Send plain text email using EmailModel? I currently have a plugin that's successfully sending email using EmailModel(). The problem is: it's sending a multi-part email with HTML and plain text components. For this particular email, it would be best if I could just send the plain text portion.

Is there a way to disable the HTML segment when sending via EmailModel()?
Currently not.  If Craft sees that there isn't anything specified for the htmlBody property of EmailModel will run the body property though Markdown and set that to htmlBody.