I sent it from my Gmail, which I indicated on my sponsor forms. I received AOR and SA to that account. But he listed a different email on his applicant forms, which is how they got in touch with him about the additional documents request.
the auto-reply says this:
"If this is a request for case specific information the responsibility placed on us by the Privacy Act to protect all personal information precludes us from responding using e-mail unless we are able to verify that you are entitled/authorized to receive the case specific information. If you are not the applicant or you are not authorized to receive the information, you will not receive a further reply to your e-mail."