Exchange Web Services (EWS) provides the functionality to enable client applications to communicate with the Exchange server. EWS provides access to much of the same data that is made available through Microsoft Office Outlook. EWS clients can integrate Outlook data into Line-of-Business (LOB).
For EWS, Exchnage cartridge provides a rule "EXC Web Services Request/sec" to monitor the counter Win32_PerfRawData_MSExchangeWS_MSExchangeWS.RequestsPersec. The EWS status will show as warning if any web service alarm fire.
Since this counter is deprecated in Exchange 2016, EWS state shows as N/A in Server status view.