Delivery Status Notification (DSN) messages are system messages generated by transport servers that inform the sender of a message about its status. When a message cannot be delivered to a recipient, Exchange will respond to the sender with a message that is associated with a status message. Sometimes, these status messages may not be detailed enough for your liking. In those cases, you can create new messages associated with the DSN code to provide more details to the sender. This is something that has to be done from the Exchange Management Shell.
You can use the New-SystemMessage cmdlet to create a custom DSN message:
New-SystemMessage -DSNCode 5.1.1 ` -Text "The mailbox you tried to send an e-mail message to does not exist. Please contact the Help Desk at extension 4112 for assistance." ` -Internal $true ` -Language En
In this example, a Non Delivery Report (NDR) with the custom DSN message will be delivered to senders that try to send messages...