MDN

Message Disposition Notification. The MIME acknowledgment the receiver returns to confirm that they received and processed the message — the proof of completion in AS1/AS2/AS3.

Definition

The MDN is defined by RFC 3798 (May 2004) and RFC 8098 (Feb. 2017, revision). Its format is multipart/report; report-type=disposition-notification with three parts:

• A text part (text/plain) human-readable.
• A machine part (message/disposition-notification) with structured fields: Reporting-UA, Original-Recipient, Final-Recipient, Original-Message-ID, Disposition (action automatic + manual + processed/displayed/dispatched/deleted/error), Received-Content-MIC (in AS2, the SHA-256 or SHA-1 MIC of the received message).
• A message part (message/rfc822) that echoes all or part of the original message — optional.

When the MDN is signed (S/MIME PKCS #7), it becomes for EDIINT the proof of non-repudiation of receipt (NRR): by signing a MIC of the received message, the receiver attests they hold the document and cannot later deny it. This property is what distinguishes AS2 from a plain HTTPS POST.

Origin

The concept of MDN comes from RFC 2298 (1998), revised and stabilised in RFC 3798 (2004) and RFC 8098 (2017). Initially aimed at mail clients for delivery and read receipts, the MDN was adopted by EDIINT (RFC 3335 AS1, RFC 4130 AS2, RFC 4823 AS3) as the standard acknowledgment. The signed MDN is cited as the key EDIINT innovation that brings non-repudiation to internet EDI.

Example in context

Disposition-notification of a successful AS2 MDN:

Reading: automatic processing succeeded (processed), SHA-256 MIC of the received content. The MDN is signed S/MIME; the archive {`sent message, signed MDN`} suffices to prove transmission.

Related terms

• AS2 — the primary user of MDN.
• AS3 — other EDIINT member.
• Non-repudiation — the cryptographic guarantee provided by signed MDN.
• Acknowledgement — the generic notion.