How to use Queue Viewer to troubleshoot mail flow issues in Exchange Server 2003

The purpose of this article is to provide a general overview of how to troubleshoot problems that may occur with various queue views in Exchange Server 2003. The "More Information" section describes each queue, common causes of problems in each queue, and troubleshooting steps.

To open Queue Viewer, follow these steps:

1. Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
2. Expand the Servers container. The Servers container may be located under the Administrative Groups container, depending on the options that are enabled on your server.
3. Expand the server that contains the queues that you want to view.
4. Click Queues to start Queue Viewer.

All transport queues are listed, including all of your Simple Mail Transfer Protocol (SMTP) virtual servers, and the message transfer agent (MTA) and the X.400 queues.

Click the Settings button at the bottom of the Queue Viewer window to select an auto-update interval for the screen. You can also update the Queue Viewer screen manually. To refresh the Queue Viewer screen, click Queues in the left pane, and then press the F5 key.

On the Actions menu for individual queues, there are two options:

• Freeze Messages: Stops delivery of all messages that are in the queue.
• Unfreeze Messages: Permits the delivery of messages that are in the queue to resume.

You can also force queues that are in retry status to immediately try again.

You can update review each queue and perform actions on messages that are queued by following these steps:

1. Click the queue that contains the messages that you want to control.
2. Right-click the queue, and then click Find Messages.

You can delete the message and choose to generate or to not generate a delivery status notification (DSN) message. You can stop delivery of an individual message, or release the message for delivery again.

You can obtain additional information about these queues by increasing the level of diagnostic logging for various categories. The following procedure uses the MSExchangeTransport service and the MSExchangeDSAccess service as examples. To increase the level of diagnostic logging, follow these steps:

1. Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
2. Expand Servers, right-click Your_ Server_Name (where Your_ Server_Name is the name of your Exchange Server computer), and then click Properties.
3. Click the Diagnostics Logging tab, and then click MSExchangeTransport.
4. In the Categories section, click a category that you want to log.
5. In the Logging Level area, click to increase the level of logging for the category.
6. Repeat steps 3 through 5 for the MSExchangeDSAccess service, and for each additional category that you want to log.

Queues

The following information is a list of the queues that are available in Exchange Server 2003. The list includes descriptions and general troubleshooting information for common issues.

Queue: Messages pending submission
First Available: Exchange 2000 Service Pack 2
Description: This queue holds messages that have been acknowledged and accepted by the SMTP service. Messages that are in this queue have not been processed.
Troubleshooting: If messages are constantly accumulating, you may have a performance problem. Occasional peaks in CPU performance can cause messages to appear in this queue intermittently. Frequently, problems with event sinks (for example, custom SMTP processing code for antivirus screening and for disclaimers) cause messages to accumulate in this queue.

Queue: Messages awaiting directory lookup
First Available: Exchange 2000
Description: This queue contains messages to recipients who have not yet been resolved against the Microsoft Active Directory directory service. Messages are also held in this queue while distribution lists are expanded.
Troubleshooting: Generally, messages accumulate in this queue because the advanced queuing engine cannot categorize the message. The advanced queuing engine may not be able to access the global catalog servers or to access the recipient information. Or, the global catalog servers are unreachable or are performing slowly. Increase diagnostic logging for the MSExchangeDSAccess service and for the MSExchangeTransport service to collect information about Categorizer components. To increase diagnostic logging for a component, review the steps that are listed earlier in the "More Information" section of this article.

Queue: Messages waiting to be routed
First Available: Exchange 2000
Description: This queue holds messages until their next-destination server is determined. The messages are then moved to their respective link queues.
Troubleshooting: Messages may accumulate in this queue if Exchange routing problems exist. For example, message routing may be backed up. Disable any unnecessary connector restrictions because the restrictions can cause a significant degradation in server performance. You may have to turn on the CheckConnectorRestrictions registry key for some restrictions.
For additional information about this registry key, click the following article number to view the article in the Microsoft Knowledge Base:
Also, increase diagnostic logging for the MSExchangeTransport service for the Routing category component to gather additional information. To increase diagnostic logging for a component, review the steps that are listed earlier in the "More Information" section of this article.

Queue: Local delivery (the domain name may appear)
First Available: Exchange 2000
Description: This queue contains messages that have been queued on the Exchange Server computer for local delivery to an Exchange mailbox.
Troubleshooting: Messages may accumulate in this queue if the information store is not accepting messages for local delivery. Slow or sporadic message delivery can indicate that a looping message or that a performance problem exists. Increase diagnostic logging for the MSExchangeIS service and for the MSExchangeTransport service for the SMTP Store Driver components. To increase diagnostic logging for a component, review the steps that are listed earlier in the "More Information" section of this article.

Queue: Remote delivery queue (this queue contains the name of the connector or of the destination server with the domain)
First Available: Exchange 2000
Description: This queue contains messages that are destined for a remote delivery. The name of the queue matches the remote delivery destination.
Troubleshooting: If the queue is in a retry state, click the queue to review the Additional Queue Information. This information is located at the bottom of the right pane. Use the NSlookup utility to review possible issues with Domain Name System (DNS) resolution. For connection and protocol issues such as "host unreachable" errors, use Telnet.exe to try to connect to the destination computer. To troubleshoot protocol errors, increase diagnostic logging for the MSExchangeTransport service for the SMTP Protocol component, and review the logs for errors. Alternatively, you can use the Network Monitor tool to obtain information about network connection errors. To reproduce the problem, you may have to force the queue to try again. To increase diagnostic logging for a component, review the steps that are listed earlier in the "More Information" section of this article.
For additional information about how to use Microsoft Network Monitor, click the following article number to view the article in the Microsoft Knowledge Base:
For additional information about the NSLookup utility, click the following article number to view the article in the Microsoft Knowledge Base:
For additional information about how to use Telnet to troubleshoot connectivity problems, click the following article number to view the article in the Microsoft Knowledge Base:

Queue: Messages with an unreachable destination
First Available: Exchange 2000
Description: Messages in this queue cannot reach their final destination server. For example, Exchange cannot determine a route or a connector to the final destination, or all available routes or connectors are marked as down.
Troubleshooting: Messages can accumulate in this queue if no route exists for message delivery. Also, if an Exchange connector or a remote delivery queue is unavailable or if it is in a retry status for a while, and no alternative available route exists to the connector or the remote destination, new messages may be moved to this queue. The administrator can then address the problem or define an alternative route. Use the WinRoute tool to help determine available routes and route status. For additional information about the WinRoute tool, click the following article number to view the article in the Microsoft Knowledge Base:
To troubleshoot the queue that is causing this issue, restart the SMTP Virtual Server to reset the connector status and to retry the messages that are queued. To restart the SMTP virtual server, follow these steps:

1. Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
2. Expand the Servers container, expand your Exchange Server computer, expand Protocols, and then expand SMTP.
3. Right-click the SMTP virtual server, and then click Stop.
4. Right-click the SMTP virtual server again, and then click Start.

Queue: Messages queued for deferred delivery
First Available: Exchange Server 2003
Description: This queue contains messages that are queued for later delivery. It includes messages that were sent by older versions of Microsoft Outlook when this option is set. Newer versions of Outlook queue these types of messages in the information store. These messages remain in this queue until their scheduled delivery time.
Troubleshooting: The following conditions can also cause messages to accumulate in this queue:

• A message is sent to a user’s mailbox while the mailbox is being moved.
• The user does not yet have a mailbox, and no master account security ID (SID) exists for the user. For additional information about disabled user accounts, click the following article number to view the article in the Microsoft Knowledge Base:
  316047  (http://support.microsoft.com/kb/316047/ ) Addressing problems that are created when you enable ADC-generated accounts
• An administrator configures SMTP in a way that causes a message to loop. SMTP moves these messages to this queue. This permits the administrator to correct the problem without causing messages to immediately return with "maximum hop count exceeded" errors. Moving messages to this queue also helps to prevent too many performance hits to the server resources.

Queue: DSN messages pending submission
First Available: Exchange Server 2003
Description: This queue contains delivery status notifications (DSN) that are waiting to be rendered by Exchange. Delivery status notifications are also known as non-delivery reports (NDR).
Troubleshooting: Messages can accumulate in this queue when any of the following conditions exist:

• The Information Store service is unavailable or is not running.
• A private information store is not mounted.
• Issues exist with the IMAIL Exchange store component. IMAIL is the component that performs message conversion.

Review the Windows application event log for errors in the Microsoft Exchange Information Store service.

Queue: Failed message retry
First Available: Exchange Server 2003
Description: Messages that failed a queue submission are moved to this queue. Frequently, messages fail a queue submission before any other processing has been done. By default, messages in this queue are reprocessed in 60 minutes. Corrupted messages or low system resources can cause messages to appear in this queue.
Troubleshooting: Review third-party programs that are installed or event sinks that can interfere with message queuing or message fidelity. If the computer responds slowly, use Windows Task Manager to determine processes that may use too many system resources. Restarting the Internet Information Server service may provide temporary relief until you can determine the root cause of the problem. To restart the Internet Information Server service, follow these steps:

1. Click Start, and then click Control Panel.
2. Double-click Administrative Tools.
3. Double-click Services.
4. Right-click Internet Information Server, and then click Restart.

Queue: SMTP Mailbox Store (X.400)
First Available: Exchange 2000
Description: This queue contains messages that are processed by the SMTP components. Messages that have been received and processed by the message transfer agent (MTA) must also be processed by the SMTP components, even if the message is destined for remote locations that are serviced by the MTA. To submit messages to SMTP, the MTA puts the messages in the SMTP mailbox inside the information store.
Troubleshooting: Make sure that at least one mailbox store is mounted and that the Microsoft Exchange Information Store service is started. To troubleshoot protocol errors, increase diagnostic logging for the MSExchangeMTA component. To increase diagnostic logging for a component, review the steps that are listed earlier in the "More Information" section of this article.

Queue: PendingRerouteQ (X.400)
First Available: Exchange 2000
Description: This queue contains messages that are waiting to be rerouted after a temporary link outage has occurred.
Troubleshooting: Messages can accumulate in this queue if a route is unavailable to a connector, to a different mail system, or to an Exchange 5.5 computer.

For additional informationabout how to view the queue in Microsoft Exchange Server 2000, click the following article number to view the article in the Microsoft Knowledge Base: