Many people still prefer plain text email. I certainly do.
I also cringe when I purple text in Comic Sans, as well as other unmentionables.
Yet, when I want to emphasize something, I hate using asterisks. It's not semantically correct, and it looks ugly. And how do you differentiate between underline and italics?
For this reason I support HTML email.
I much prefer plaintext only mails. Not only are they readable on any device, I also don't have to be afraid of getting my machine infected by who-knows-what.