Abstract: Systems and methods for authenticating a message receiver and for authorizing the authenticated receiver to manipulate the received message are disclosed. Various message delivery mechanisms and sender authentication mechanisms are used to perform receiver authentication. When a message (message A) is delivered to the receiver, the receiver cannot view or manipulate the message until the receiver is authenticated by the sender or by a sender-authorized third party. In this system, the receiver sends out a message (message B) to the sender to indicate the reception of the message A. Message B is then authenticated using a sender authentication mechanism. Once Message B is authenticated as coming from the intended receiver, the sender of message A authorizes the appropriate privilege for the receiver to manipulate message A.