From the FAQ webpage:
"In most cases, official notification that a decision has been made is delivered by e-mail. For security, such e-mail does not contain the decision itself however. Decision information will be posted in the on-line application. Decisions are made and communicated during the months of February and March. Official decision notification is made by the Graduate School and not individual departments or programs. Only letters or e-mail sent directly from the Graduate School may be considered official notifications of admission and financial aid. The Office of Graduate Admissions cannot give decision results over the phone.It is important that you keep both your e-mail address and mailing address current. Any changes necessary can be made from within your on-line application".