The following guidelines for Performance Monitor counters are taken from a very large, complex organization messaging system with over 45,000 messaging system users. Note that these results can vary by a wide margin in different environments. Variables such as network infrastructure, messaging system user profiles (such as light, medium, or heavy users), and topology affects the outcome of the counters below.
MSExchangeMTA, Work Queue Length The level should increase and decrease. An acceptable range would be 0-50. When messages are stuck in the queue, the counter will remain level, or only increase for extended periods of time. Watch for artificial floors on the MTA queue. Used here, artificial floor means the work queue length remains at or above a non-zero, positive integer. This could mean that there are corrupt or stuck messages in the queues, or it could simply mean your queues house a number of messages that have been sent with the deferred delivery option in Microsoft Exchange Clients.
MSExchangeMTA, Messages Delivered per Minute This counter measures the rate of the number of messages being delivered by the MTA to the information store. Normal load is 10-40 messages per minute. If this number is constantly under 5 per minute when there are pending items in the MTA queue, then it is likely the server is under severe load or there is a problem with one of the processes. If this number is extraordinarily high (greater than 200 per minute) for an extended amount of time, then it is likely that there is a stuck message in the MTA queue.
Microsoft Exchange Server services processes This is the object: Process, Counter: % Processor time, Instances: DSAMAIN, EMSMTA, MAD, and STORE. No object should be at 0 percent or at 100 percent all of the time. An object always at 0 percent indicates a dead process. Check Service Control Manager to verify that the service is running. An object always at 100 percent usually indicates that something is out of order. Check other services and the Windows NT Event Viewer to pinpoint the problem.
Paging File, % Usage Make certain that the usage is in a reasonable range, generally 15-35 percent. When the level of usage exceeds 60 percent, there is usually something wrong. If the usage constantly exceeds 90 percent, then the situation needs to be treated as a problem. There is either a problem with one of the processes, the server needs to have a RAM upgrade, or the paging file was incorrectly allocated during setup.
LogicalDisk, Free Megabytes, Instance: E This is the amount of free space on the transaction log drive. Monitor this object to ensure that the drive does not fill up with .log files. Normally, the .log files are removed whenever an online backup is performed. If the .log files are not being removed, verify that the backups are being done correctly and completed successfully.
MSExchangeIS, Active Connection Count This measures the number of logons to the information store service. This number should be greater than zero. If the server has active mailboxes and there are zero connections, then a problem exists. Use a test account to see if there is a problem making a connection to the server.
MSExhangeDS, Pending Replications Shows the number of replication objects yet to be processed.
MSExchangeDS, Remaining Replication Updates Measures the number of objects being processed by the directory service. This number usually starts at 100 and decreases to 0 within 1 to 3 minutes.