Configuring Diagnostic Logging for SMTP
To help you determine the cause of a transport issue, you can view events that relate to MSExchangeTransport. If you experience problems with Exchange message flow, immediately increase the logging levels relating to MSExchangeTransport. Logging levels control the amount of data that is logged in the application log. The more events that are logged, the more transport-related events that you can view in the application log. Therefore, you have a better chance of determining the cause of the message flow problem. The SMTP log file is located in the Exchsrvr\Server_name.log folder.
As discussed in "Using SMTP Queues to Troubleshoot Message Flow" and "Using X.400 (MTA) Queues to Troubleshoot Message Flow," issues with specific routing and transport components can cause messages to accumulate in a queue. If you are having problems with a specific queue, increase the logging level for the component that is affecting the queue.
For detailed instructions, see the following procedures: