Software agents perform a process to monitor the availability and/or performance of various functions of a messaging system, such as a Unified Messaging System. A call is initiated to an endpoint, where the endpoint is registered with a messaging system and is configured to forward incoming messages to the messaging system. A first agent transmits a message to the endpoint for forwarding to the messaging system. A second agent that is associated with the endpoint then determines whether the endpoint receives a message notification in response to the transmitted message. In an embodiment, the time that elapses between arrival of the message at the endpoint and reception of a message notification is determined. In an embodiment, if the second agent is able to access a mailbox and retrieve the transmitted message, then the message retrieved from the messaging system is compared with the version of the original message that was received at the endpoint. Whether the retrieved message suffered any degradation from its path through the messaging system is determined based on the comparison.