As a temporary fix, I added a <html>%0D%0A at the start of the body portion of the email and a %0D%0A%</html> at the end. Unfortunately, the tags show as text in the body, but everything is on its own line.
...body=<html>%0D%0ALine1%0D%0ALine2%0D%0ALine3%0D%0A</html> shows up as:
<html>
Line1
Line2
Line3
</html>
I don't like the <html> and </html> showing up, but at least the body is once again readable.