Interview related documents submission prior to interview date.. any acknowledgement?

[High5]

The consulate in mumbai requires some documents to be submitted 3 days in advance of the interview date. I was wondering if the consulate gives any acknowledgement receipt after they have taken the documents prior to the interview date. How do we make certain that the documents have reached them 3 days before the interview if we are planning to send it to them through a friend's distant relative.