XFOR: Retiring an Internet Mail Service (285090)

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It is a common misunderstanding that if you stop or disable an unused Internet Mail Service, the service is taken out of commission and messages are not lost. It is also a misconception that if you set the transfer mode of an Internet Mail Service to None or Inbound Only, messages from the Exchange Server organization are not routed to outbound destinations. However, this is not the case. In both cases, messages can still be routed to the disabled Internet Mail Service and continually be queued in the XAPI mailbox on the server that houses the retired Internet Mail Service. When messages arrive in the Internet Mail Service mailbox (MTS-OUT queue), the message transfer agent (MTA) is not able to reroute them to other destinations, and non-delivery reports (NDRs) are not generated. Therefore, if the Internet Mail Service that you disabled is never started again, the messages are lost.

To prevent messages from being sent to an Internet Mail Service that has been taken out of commission, use the following method to retire the Internet Mail Service:

1. If an MX record points to an Internet Mail Service that has been taken out of commission, modify the MX record so that it refers to another Internet Mail Service in your organization that receives inbound Internet mail.
2. On the Internet Mail Service, set the transfer mode to Outbound Only, and then restart the Internet Mail Service so that all outbound mail messages are sent. The Internet Mail Service then no longer accepts inbound mailflow; this mail must be sent to another inbound Internet Mail Service.
3. Remove the address space from the Address Space tab in the Internet Mail Service properties. Messages are then no longer routed to this connector, and the MTS-OUT queue does not grow.
   

Monitor the retired Internet Mail Service for a few days to ensure that the previous Internet Mail Service settings have been transferred, and that no issues develop if this Internet Mail Service is taken out of commission. If no issues have occurred in a few days, it is safe to remove the Internet Mail Service from the computer.