I broke down and called the number at the bottom of the email, the Department of Scholarships and Admissions. At first the lady I spoke with seemed to indicate this MUST mean I've been accepted, but then she backpedaled when I asked if she was sure, had proof in front of her, etc. She transferred me to the Office of the Graduate School, who were very perplexed about the email having been sent out, and reported that their phones had been ringing off the hook all morning with similar inquiries.
Ugh. I'm attempting to not be frustrated, but I'm failing at it...