Our client has recently upgrade to Exchange 2013 and our software uses EWS to create appointments using impersonation.
There are 12 combination role servers, 10 servicing EWS calls. For now they've mapped a specific machine in our servers hosts file to bypass the load balancer so we are hitting a single CAS server. Our service accesses a subset of approx. 150 users spread across these servers.
When making requests/calls to EWS with impersonation we keep getting "Active Directory operation did not succeed. Try again layer". The issue exists whether we go through the load balancer or not.
It is sporadic in that it works some days and other days we get constant failures and haven't been able to narrow down the issue. Should we be concentrating on the AD servers or exchange servers to isolate the problem..
The following throttling policies applied to our system account is as follows:
EwsMaxConcurrency : Unlimited
EwsMaxBurst : Unlimited
EwsRechargeRate : Unlimited
EwsCutoffBalance : Unlimited
EwsMaxSubscriptions : Unlimited