"Test E-mail Autoconfiguration" for outlook
1. Hold Control Key and Right click outlook icon bottom right of the task bar. It might be possible that Outlook Icon is hidden in Notification bar. If it is so Click and drag icon into task bar.
2. From Popup-menu Test E-mail Autoconfiguration.
3. Select only “Use AutoDiscover” and then click Test button
Similarly you can check the "Connection Status" to check which GC/CAS/FE server Outlook is connected to.
Here is the Image of both of the Options