A method for monitoring performance of a message-delivery system, such as an SMS delivery system for instance. According to the method described, key performance metrics will be collected from one or more message-routers and will be monitored over time to determine when a threshold problem condition occurs with the message-delivery system. In response to detecting a threshold problem condition such as (i) a threshold measure of difference in router-input and router-output, (ii) a threshold measure of change in message-queue length, and/or (iii) a threshold measure of message delivery attempts per message, an alert will then be generated, in order to inform network administrators or systems of a potential issue and to allow prompt remedial action to be taken.