There are two parameters that (potentially) influence report of missing receipts:
Parameter 1: the ebMS3 Core Specification defines PMode.ErrorHandling.Report.ProcessErrorNotifyProducer as: This Boolean parameter indicates whether (if "true") the Producer (application/party) of a User Message matching this P-Mode should be notified when an error occurs in the Sending MSH, during processing of the User Message to be sent.
Parameter 2: AS4 defines a new PMode.ErrorHandling.Report.MissingReceiptNotifyProducer to control the behavior of a Sender that failed to receive a Receipt (even after message retries) with AS4 Reception Awareness.
An error caused by a missing receipt is just a special case of an error in the Sending MSH, so it is unclear why this error needs a special parameter. It also raises the question how the parameters relate, e.g. if P1 is set to false, can P2 still be set to true, signalling a kind of override of the core parameter only for missing receipts? If P1 is set to true and P2 to false, are missing receipts not notified, unlike all other errors in the Sending MSH?
One reason for a new parameter could be that Reception Awareness is a new feature and that therefore somehow reporting on it is not covered by ebMS3 implementations that are not (explicitly) also AS4 implementations. But there are two other new errors (for invalid receipts and decompression errors), for which there are no new parameters, e.g. there is no PMode.ErrorHandling.Report.InvalidReceipttNotifyProducer and no