If it means anything, last year the website also said email for waitlist/rejections and snail mail for acceptances, but ALL notifications went out via email (wait/rej/acc) on March 15.
My heart dropped when I saw an email from Duke in my inbox, thinking it could only be bad news, but what a complete 180 when i actually opened it 🙂
I have no idea what the date will be (March 5 seems to be consistent based on what you guys have been told), but I strongly suspect that ALL decisions will be electronically conveyed on that date. Acceptances will of course get snail mail later on with all the instructions for deposits and whatnot.
Not sure if that clears anything up or makes it worse since I don't know for sure...but there you have it.