Exchange and other MTAs use DSNs (Delivery Status Notifications) and NDRs (Non-Delivery Reports) to notify the sender or sending MTAs (Message Transfer Agents aka Mail Servers) about the various statuses of a given email message. In Exchange, those messages are generated primarily by the categorizer component of the transport service.
You can use the New-SystemMessage cmdlet to create new messages. These messages can even be localized and can contain Html tags for properly styled notifications.
From a system perspective, the various notifications used are named and fulfill a specific purpose.
Report and receipt types (Exchange Version independent) used for notification
- Delivery Receipt (DR)
A report confirming that a message was delivered to its intended recipient
Delivery Status Notification (DSN)
A report describing the result of an attempt to deliver a message
Message Disposition Notification (MDN)
A report describing the status of a message after it has been successfully delivered to a recipient. Examples: read notification (RN) or non-read notification (NRN)
Defined by RFC 2298 and controlled by Disposition-Notification-To header
Non-Delivery Report (NDR)
A report indicating to the message sender that the message could not be delivered to the intended recipients
Non-Read Notification (NRN)
A report indicating that a message was deleted before it was read when a read receipt was requested
Out Of Office/Facility (OOF)
A report indicating that the recipient will not respond to a new message
OOF refers to the Microsoft original term „out of facility“
- Read Notification (RN)
A report indicating that a message was read
- Recall Report (RR)
A report indicating the status of a recall request for a specific recipient
A recall request is used when a sender tries to recall a sent message by using Outlook