Use the Get-ConnectionByClientTypeReport cmdlet to view a summary of the different types of clients that connected to all mailboxes in your organization. The client types indicate different protocols, for example, Outlook on the web, MAPI, POP3, IMAP4, Exchange ActiveSync, and Exchange Web Services.

https://technet.microsoft.com/en-us/library/jj873753(v=exchg.160).aspx