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Understanding Queues in Exchange Server:

We don’t see messages in the queue usually, as they get processed & routed quickly by the Exchange Server. Messages remain in the queue if there is any problem or if the message has been suspended by an administrator for some reasons.

If we see a lot of messages in the queue & if it keeps increasing, then there is definitely a problem! We can get the summary of the currently available messages in the server by clicking the “Queue” tab in the Queue viewer. The queue summary providers some important details that are required to troubleshoot the issue. So to analyse a problem we need to look at the connection status & the values will tell us the state of the queue.

Queue Connection Status:

Active Queue: This queue has messages that are being transported.

Ready Queue: This queue is required to allow all messages to be transported. Basically when the queues are ready, they have a connection to process the message.

Retry Queue: This queue has messages that fails to connect & the server is waiting to retry.

Suspended Queue: This queue has messages in suspended state & it cannot be processed for routing.

So the above are the various connection status of the queue. It can be controlled by an Administrator if he wants he can right-click & suspend a message, similarly he can change the queue status to active by right clicking & resume. Also we can right click a message & click Retry if it’s not getting processed, this operation enables Exchange to try to process that message in retry state.

Apart from the above queue connection state, we also can get other summary information from the following:

Delivery Type: This tells us for what type of recipient messages are being queued for delivery.

Next Hop Domain: This tells us the next destination of the delivery queue. For the remote delivery queues & the mailbox delivery queues, this tells the next hop domain. Also the messages that are queued for delivery to an EdgeSync Server lists the associated site & the destination. (eg:EdgeSync–Default-First-Site To Internet).

Message Count: This tells us the total number of messages waiting in the queue. If we a large number of messages waiting in a queue, that keeps building up, it indicates a routing problem.

Next Retry Time: This tells us when the next connection attempt will be made in scenarios where the connection state is retry.

Last Retry Time: This gives information about when the last retry attempt was made.

Last Error: This tells us the error code & the details of the last error. When we have any message delivery problems we can make use of this last error code details or troubleshooting the issue.

Refreshing the queue:

The above queue status will provide information to find the message queuing problems. Br default the queue viewer is refreshed every 30 seconds. The maximum number of the message item that can be listed on each queue viewer page is 1,000.

To change the Queue Refresh settings:

  • Open Queue Viewer => on the View Menu => Click Options.
  • To turn off the automatic refresh => clear the “Auto-Refresh Screen” check box.
  • In the Refresh Interval text box we can type a specific refresh rate in seconds.
  • We can type the desired maximum number of messages to be displayed per page in the “Number of Items to Display text box”. Click OK.


Working with messages that are in the Queue:

In order to manage the queues we need to enumerate messages, this process allows to view the queue content & perform the administering tasks on it. This can be achieved by simply double-clicking the specific queue & viewing the individual messages. We can also create filters for specific type of messages. To create filter:

=> Click create filter.

=> Click the first selection list to specify the field we want to filter the messages with. We have various options to filter a message like: Date Received, Expiration Time, From Address, Internet Message ID, Last Error, Message Source Name, Queue ID, SCL, Size (KB), Source IP, Status, and Subject.

=> We can use the Second selection list to match the search criteria using: Equals, Does Not Equal, Contains, Does Not Contain, Greater Than, and Less Than.

=> Next we can use the text box to specify the exact search criteria to match.

=> Finally click “Remove Expression” button to stop filtering.

Forcing, Resuming & Suspending Queue:

As we already saw, we can force connection to a message in queue by Right clicking & force connection. Similarly we can resume & suspend a queue.

When we suspend a queue all new message transfer activity out of that queue stops and only messages being processed will be delivered. Which means all the new messages will continue to enter the queue but will not leave the queue. Also if you suspect a large message to be causing issues, you can specifically suspend that message in the queue to find out the problem. This operation is similar to the above, simply enter a queue, right click on the specific message & click “suspend”. We can select multiple messages using the Shift & ctrl option.

Deleting Messages from Queues:

We do have option to delete the message in the queue if required. The following are the steps to delete a message:

=> Queue Viewer => select the queue we need => double-click the queue to open all message inside the queue => right click & delete the message, we can use shift & ctrl option to select multiple messages at a time to delete.

=> When we remove message we have the following options, administrator can select either of the one that is appropriate:

Remove (With NDR) Deletes the selected messages from the queue, and notifies the sender with a nondelivery report (NDR)

Remove (Without Sending NDR) Deletes the message or messages from the queue without sending an NDR to the sender

A very important point to note is that when deleting a message from the queue, it deletes the message permanently & it cannot be recovered. So we have to very careful while performing such action.

Ratish Nair

Microsoft MVP | Exchange Server

Team @MSExchangeGuru

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