When Exchange is misbehaving, we usually check the Application/System Logs in Event Viewer. You better enable highest level of Exchange diagnostic logging to get more details of your problem.
Follow the steps below to increase or decrease the diagnostic logging and analyzing the Event logs.
1. Increase Application Event Log size to 75 MB on your Exchange (bridgehead) servers
2. Open Registry Editor on your Exchange bridgehead servers. Open the following location,
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServices<Exchange Service Name>Diagnostics
3. Open every key on this location and enter value "7" like below (image shows MSExchangeTransport diagnostic options)
4. Close the Registry Editor.
Now Exchange will create more logs of selected diagnostic logging.