The Event Relay Server expects to receive an XML response message for each notification sent to the external application. Depending on the response received, the message is logged by the ERS as successfully sent or needing to be resent.
If the listening application receives the message, the ERS logs the transaction depending on the XML response. If the listening application cannot be reached by the ERS, the transaction is logged based on the HTTP status response received. How the ERS handles these responses is explained in the sections below.