I put in my fiance's passport number and received the message:
"Your passport has been handed over to Blue Dart for delivery on 16-Apr-2007. Click here for Status."
That was indeed the correct date of his visa (stamped in the passport) and the date it was mailed. I clicked to see the status and received the message:
"Waybill No : --- Ref No : ---
Status: Incorrect Waybill number or No Information
Status Type: NF"
It was delivered in hand to my fiance on April 17th, but this message doesn't reflect that.
That's my story; others can experiment to see if it works!