Why doesn’t Get-LogonStatistics give me any information about OWA?
Some of you may have found and indeed been confused by the fact that when using the Get-LogonStatistics cmdlet within your Exchange installation does not return any information about users whom are currently logged on via Outlook Web App.
This is by design as OWA sessions are not continuously connected to a Mailbox server.
In essence OWA will connect, authenticate perform user actions and then disconnect.
If you need to get information in regard to OWA connections, the best bet is to you the Performance Monitoring Tool (PerfMon) using the MSExchange Web Mail performance object and review the Authentications (in cache) or use the Exchange Server User Monitor