This week I received a question via e-mail about an Exchange 2010 environment. In this environment some big problems did occur which caused a large amount of messages to be placed in the Unreachable queue. Messages will be placed in the queue when Exchange can’t deliver the messages. This can be both messages which need to be sent to external mailservers or internal Exchange servers.

The queues can be viewed via two methods:

  • via the queue viewer
  • via the Powershell cmdlet get-queue

Using the first method you can also view specific messages which are located in a queue. By default some attributes will be registered from each message among them:

  • sender
  • receiver
  • subject
  • date and time

You might chose to export the messages and import them again to a queue. But in most cases this will not be a suitable solution when hunderds or maybe thousands of messages are located in a queue.

In this kind of scenarios you can better use the Retry-Queue cmdlet. Using this cmdlet messages are resubmitted to the categorizer. Two things this component is responsible for is searching the address of the recipient and route messages. To route a message correctly a message is placed in a queue which is used to deliver the message to the recipient. When you are having a look in the queue viewer you will see several queues among them a queue for each mailbox database. Besides this, queues can be found which are used to deliver messages to the internet. When using a smarthost only one queue will be seen here which is used to deliver messages to the internet.

When messages can’t be delivered in a specific time range messages will be placed in the Unreachable queue. This can for example happen when the mailbox server is not reachable.

To resubmit this messages you will need to use the following cmdlet:

Retry-Queue -Identity <servername>\Unreachable -Confirm -Resubmit $true

For example:

Retry-Queue -Identity HUB01\Unreachable -Confirm -Resubmit $true

In the example above all messages from the Unreachable queue on the server HUB01 will be resubmitted.

After running the cmdlet the messages will be delivered. Depending on the amount of messages this may take some time.

For more information have a look at the page below.:

Technet: Resubmit Messages in Queues open


Johan Veldhuis