@mitch y'all know some people read the plaintext and never even see the HTML?
I got an email saying my appointment was cancelled and I'd have to reschedule. Annoying, but whatever - until they called me to try and ding me for a no-show fee. Turns out their marketing dingbats just edited an existing email to avoid having to compose it from the ground up, and they changed the HTML attachment but not the actual text of the email. And their starting point was the "appointment cancelled" message. >:(