Did the rules on capitalization change when I wasn't looking?

I've been encouraging my students to email me this term, and a surprising number of them are using what can only be described as random capitalization, when they can manage to find the shift key at all. I know that many people perceive email as a relatively informal style of communication, but really, when a student is emailing someone who has the power to assign him or her marks, don't you think it might occur to the student that it might be a good idea to capitalize the name of said person?