Yea, that should be fine. I'd recommend calling the admissions office and asking, that will get you a definite answer. All schools have different policices with LOIs and updates and stuff like that. Maybe theyll want you to send it via snail mail? Just call and ask.
WARNING: If you do send a LOI or anything via email, CHECK UP ON IT to make sure that it was received. I didn't check on a LOI that I sent, and a month later I got an email saying "oops, this email got lost and we never read it so the LOI was never added to your file." Kind of irritating, but could have been resolved if I had just followed up on the email.