How is a bounced message routed?
A bounced message is routed as follows:
- If the recipient address is invalid, the message bounces back to the sender.
- If the sender address is also invalid, the message bounces back to the recipient domain's Postmaster.
- The recipient domain's Postmaster sends the mail to the sender domain's Postmaster.
- If the sender domain does not have a Postmaster responsible for this type of bounced message, the message is again bounced back to the recipient's domain Postmaster for final delivery.
NOTE: As of Release 3.1, a limit is imposed on the number of delivery status notification (DSN) messages that are sent to one sender in a domain. When this limit is reached, a final DSN message is sent saying that no more status messages will be sent today. After this occurs, a count is kept of each sender, domain, recipient, and reason. The collected DSN information is sent out early the next day. The default Dsnlimit is 100; zero (0) indicates no limit and no summary message. The default value for this limit can be adjusted using the Smtp Set Dsnlimit command.