Ali,
In MSP the receipt is recipient generated, not delivery
MTA-generated, so whether the recipient gets to read the message prior to
sending the receipt is a function of the local MSP implementation. In
general, it will not be possible to prevent a recipient from reading first
and sending the receipt later, or not sending the receipt at all. For the
MSP environment (e.g., the Defense Message System) it was deemed more
important to provide timely delivery than to insist that delivery not
succeed until delivery of a receipt could be guaranteed. The Tygar
approach to receipting is more stringent in the security guarantees it
offers, but it also is more time consuming and it generates more message
exchanges.
Steve