Exchange Properties of users are not getting open for some users


We are recently facing the issue on few users for whom we are not able to open exchange properties. Other tabs are working fine, but when we select exchange properties in ARS portal after opening user general properties, it takes time and finally terminate with timeout.

We have few recent changes in our environment and I am suspecting that change or may be exchange server my ARS is configured to access is down, not sure.

Can some one tell how can I check which exchange server (CAS Server), my ARS portal accessing and how can we change the name in ARS server to target another one?

I am using ARS 6.9.