For Checking OWA Connection Count
Get-Counter “MSExchange OWACurrent Unique Users” -ComputerName SERVER1,SERVER2, SERVER3
For Checking MAPI Connection Count
Get-Counter “MSExchange RpcClientAccessUser Count” -ComputerName SERVER1,SERVER2, SERVER3
For Checking OWA Connection Count
Get-Counter “MSExchange OWACurrent Unique Users” -ComputerName SERVER1,SERVER2, SERVER3
For Checking MAPI Connection Count
Get-Counter “MSExchange RpcClientAccessUser Count” -ComputerName SERVER1,SERVER2, SERVER3