If you navigate to the Exchange’s ProbeResult Crimson Channel of ActiveMonitoring, you will likely find the following error event logged:
Error: Failed by design.
Exception: System.Exception: Failed by design. at Microsoft.Office.Datacenter.ActiveMonitoring.TestActiveMonitoringProbe.DoWork(CancellationToken cancellationToken) at Microsoft.Office.Datacenter.WorkerTaskFramework.WorkItem.Execute(CancellationToken joinedToken) at Microsoft.Office.Datacenter.WorkerTaskFramework.WorkItem.<>c__DisplayClass2.<StartExecuting>b__0() at System.Threading.Tasks.Task.Execute()
So why is something failing by design?! Basically this probe is testing the Managed Availability framework, including that it can run responders. More specifically, a probe that will test that monitors can become unhealthy and execute null responders.
Bottom line, nothing to worry about 🙂