ERROR QuestEWSService - GetUserAvailability() System.TimeoutException (Free Busy lookup from Outl (4253847)

In some environments, there may be intermittent issues with free busy requests from Exchange to Domino direction and you may see "There server was busy" and the following error in EWS.log file on CMN server:

ERROR QuestEWSService - GetUserAvailability() System.TimeoutException: This request operation sent to net.tcp://localhost:8960/FreeBusyService did not receive a reply within the configured timeout (00:01:00). The time allotted to this operation may have been a portion of a longer timeout. This may be because the service is still processing the operation or because the service was unable to send a reply message. Please consider increasing the operation timeout (by casting the channel/proxy to IContextChannel and setting the OperationTimeout property) and ensure that the service is able to connect to the client.