A method and system in an application service provider ("ASP") system for regulating the dispatching of event notification messages that generate return contacts. The ASP system is connected to various requestor systems and receives from those systems requests to send messages to designated recipients. The ASP system dispatches the messages by retrieving the requests from the request store, generating messages for the requests, and sending the generated messages at a requestor-specific message dispatch rate. The ASP system dynamically adjusts the message dispatch rate for a requestor in real time to help ensure that the requestor is not overwhelmed with return contacts.