Electronic mail is, as has been pointed out so often in the last couple of years that it's become a cliche, the modern equivalent of the familiar century of a hundred years ago. What is not so often pointed out is that it makes written language immediately dialogic in ways that haven't been possible since the times when there were many daily mail deliveries in London. How long before you get an answer matters to how you write.
Email takes many forms, of course. In a course there are really four possibilities:
This makes it seem pretty simple. In fact, it can be extremely rich, but one of the important facts about it is that it tends to become extremely trivial, and to die off, if it's not stimulated, modeled, and made worthwhile. I'm writing an article about this tendency, and what might be done to minimize it, and promote the use of language for serious academic thought.