We've recently started using Exchange System Manager's (ESM's) built-in monitoring tools to keep an eye on some of our Exchange Server services. I've noticed that ESM sometimes tells me that a critical service isn't running when it actually is. What causes this discrepancy?

ESM uses Windows Management Instrumentation (WMI) interfaces to poll a target server's services. You can't set the polling interval, so when you use the Monitoring and Status node in ESM's Tools container to check the status of a service, keep in mind that there will be some latency that you'll need to take into account. Take a look at "Check Service Status on Local or Remote Servers," March 2004, InstantDoc ID 41670. That article describes how the WMI service monitoring interfaces work and includes a sample script that you can use to set a time granularity for monitoring the services. Furthermore, if the WMI service isn't running on the target server, ESM will report that the queried service isn't available, so be sure WMI is operational on all involved systems.