Delivery status notification
DSNs are usually triggered when e-mails are definitely undeliverable ("permanent failure").
Intermediate reports about outstanding deliveries are also common if e-mails cannot be delivered temporarily (“Persistent Transient Failure”), for example if the recipient's mailbox is full or the addressee's mail transfer agent is not available. This is then followed by either a DSN about the final failure of the delivery ("Permanent Failure") or a positive DSN about the successful delivery ("Success").
A DSN relating to an e-mail that cannot be delivered or that cannot be delivered temporarily is also known colloquially as a bounce message .
A positive DSN ("Success") will - apart from the case described above - only be sent if the sender of the original e-mail has expressly requested it, for example by setting the option "Request delivery confirmation" or "Request delivery status" ( Mozilla Thunderbird ) in his e-mail program. However, not all e-mail programs offer this option. The positive DSN shows that the email has reached the recipient's area of responsibility. In this respect, it has the character of a notification of the successful submission of a registered letter . Since a positive DSN only confirms the successful placement of the e-mail in question on the recipient's mail server, it cannot be concluded from the receipt of this DSN that the e-mail in question will actually reach the recipient or be perceived by him.
Not every mail provider supports DSNs. When the sender expects a delivery confirmation, the sender usually receives a message on delivery to a mail server that does not support DSNs, which is displayed, for example, as a "relayed to non-DSN-aware mailer" - especially if the mail is sent properly was delivered.
- Message Disposition Notification , a mandatory confirmation of receipt
Norms and standards
- RFC 3461 (successor RFCs are: RFC 3798 , RFC 3885 , RFC 5337 , RFC 6533 ).
- RFC 3462
- RFC 3463
- RFC 3464