MTA Queues

The MTA maintains queues for each message destination. This includes the MTAs of other servers in its site, the information store on its server, and any installed connectors, including RAS Connectors, Site Connectors, X.400 Connectors, Internet Mail Services, and Microsoft Mail Connectors. If the server is a replication bridgehead, the MTA will also have a queue to the directory on its server.

There are two types of queues. The type determines when you see the queue in the MTA Queues property page and whether you can change the order of messages in the queue.

Secured queues   Part of the application interface to the MTA. The MTA queues to the Internet Mail Service and Microsoft Mail Connector are secured. They do not appear in the queue list until the connector sends messages to or retrieves messages from the MTA. You cannot change the priority of messages in these queues.

Unsecured queues   Part of the MTA and appear in the queue list whenever the receiving service is running. You can change the priority of messages in this queue. MTA queues to components on its server and to Site Connectors, RAS Connectors, X.400 Connectors, and the MTAs of other servers in its site are unsecured.

Use the MTA Queues property page to determine the number of messages in each queue, to view a message in the queue in detail, to delete a pending message, and, for unsecured queues, to change the order of messages in a queue.

Getting to the MTA Queues property page

1. In the Administrator window, select a server.
2. Double-click Message Transfer Agent.
3. Select the Queues tab.

Viewing Message Detail

The message detail available in the queues can be useful for troubleshooting:

• The originator information, taken from the message heading, shows the sending or receiving server. If the same server is involved in several suspect messages, there may be a server configuration error.
• Use the MTS-ID or message ID to trace the message through the tracking log, event log, or other queues.

1. Select the Queues tab.
2. Under Queue Name, select a queue.
3. Double-click a message.

Option	Description
Originator	The location of the sender, including the host address and sender name.
MTSID	The MTS-ID or message ID.
Submit time	The time the message was submitted in local time.
Priority	The importance assigned to the message by the sender.
Size	Size of the message in bytes.

Refreshing the Queue Property Page

The MTA Queues property page is a snapshot of the queues taken when you select it. It is not updated automatically. Use the Refresh button to update your view of the queues. Secured queues appear only when there is mail to be sent to or received from them. They can appear or disappear from the list when it is refreshed.

1. Select the Queues tab.
2. Choose Refresh.

Changing Message Order

You can change the order of pending messages in unsecured queues. Messages in MTA queues to components on its server and to site connectors, RAS Connectors, X.400 Connectors, and the MTAs of other servers in its site can be reordered. This is very useful if an urgent message needs to be delivered immediately, or you suspect that a message is defective.

Use the Priority button to increase the priority of urgent messages and lower the priority of messages that might block the queue. Priority is a sort parameter. Messages with the same priority appear in the queue in the order in which they were received.

Note   You cannot change the priority of messages in MTA queues to the Microsoft Mail Connector or to the Internet Mail Service. These are secured queues. Also, you cannot change the priority of the first message in an MTA queue if it is already being transported.

1. Select the Queues tab.
2. Under Queue Name, select a queue.
3. Select a message in the queue.
4. Choose Priority, and then select a priority.

Option	Description
High	Highest priority level. If the priority of other messages in the queue is Normal or Low, setting the priority of a message to High moves it to the top of the queue.
Normal	Medium priority level. This is the default.
Low	Lowest priority level. If the priority of other messages in the queue is High or Normal, setting the priority of a message to Low moves it to the end of the queue.

Deleting Messages

Messages can be deleted from unsecured queues. Deleted messages are returned to the originator as non-deliverable. For example, you can delete a queued message if it is too large.

1. Select the Queues tab.
2. Under Queue Name, select a queue.
3. Select a message in the queue.
4. Choose Delete.

Using MTA Message Queues for Troubleshooting

You can use the information in MTA queues to resolve message delays and find missing messages.

Tip   Use the MTA Connections Queue Size counter in Windows NT Performance Monitor to alert you when messages accumulate in MTA queues. For more information, see Chapter 3, "Monitoring Your Organization."

• If a queue has more messages than expected, check the configuration of the destination server for the first messages in the queue, and search the application event log for problems with the connection.
• The Submit Time displayed in the Queues property page identifies when the MTA received the item. Compare this to the time the message was sent to determine where delays are occurring.
• If you suspect that a message will block the queue, delete the message, or, if the queue is unsecured, lower its priority to allow other messages to pass it.
• If the message being transported is blocking the queue, use your link and server monitors to make sure the receiving service is operating and that all connections are operating. Check the application event log for errors generated by the receiving service or the MTA. If you must delete the message, stop the receiving service. This releases the message so you can delete it.
• If messages are accumulating in the MTA queue to the Internet Mail Service, check the Internet Mail Service MTA Out queue to determine whether it is retrieving its messages from the queue. This is the destination for messages in the MTA queue to the Internet Mail Service.
• If an MTA queue to another service is blocked, most likely a message in the queue is corrupt, the receiving service is not retrieving its messages from the queue, or the MTA is not functioning correctly.