Recently we had a case where an Exchange 2010 Hub Transport Server was being decommissioned, we had got to a point whereby the following had been done –

  • Remove the server from the DAG
  • Removed the server from the HLB
  • Removing the server from any send connectors
  • Remove the server from OAB distribution
  • Disabled the receive connectors.

When running through the pre-requisites for uninstallation we received a warning on the Hub Transport role for mail queuing. I checked the queues and sure enough some mails had gone into the local ‘SMTP Relay for Active Directory Sites’ queue. We then found that the reason for this is due to the server being decommissioned was homed in a different AD site and mail was attempting to send via the hidden AD send connectors created on installation. Below is a TechNet article explaining this in abit more detail.

To fix this we completed the following –

  • Stop the Exchange Transport Service on the affected server.
  • Navigate to “<Install Drive>Program FilesMicrosoftExchange ServerV14Transport Rolesdata” on the same server, copy the Queue folder.
  • On a separate, working Hub Transport server – stop the Exchange Transport Service. (Please note that stopping the Transport Service will stop outgoing mail from the server the service is stopped on.)
  • On the working server, navigate to  “<Install Drive>Program FilesMicrosoftExchange ServerV14Transport Rolesdata”. Rename the queue folder to queue.old.
  • Paste the queue folder from the server being decommissioned into the working Hub Transport server.
  • Start the Exchange Transport Service again on the working Hub Transport server. Make sure you can see the queue in Queue Viewer and then watch the queue dissipate.
  • For completeness after the queue has depleted. It is safe to delete the copied folder named “queue” folder and rename the “queue.old” back to “queue” on the working Hub Transport server.

I hope this helps.