HLB Probe URLs

I am trying to setup a probe in an ace loadbalancer to detect when https Exchange services are down.

All of the examples I have found point to using /owa/auth/logon.aspx but this returns the same result regardless of whether the Exchange services are running or not, as it is just an IIS page.

Does anyone have any valid examples that return a different result via https when the Exchange services are down as opposed to when they are up.

Thanks

Tim