guide · how-to
What is an AS2 MDN, and why is it negative?
The MDN (Message Disposition Notification) is AS2's delivery receipt. When it turns negative or stops arriving, a certificate is a common culprit.
What the MDN tells you
After you send an AS2 message, the partner returns an MDN saying whether it was received and processed. A positive MDN means success; a negative one carries a reason — often signature-verification or decryption failure.
When it points at a certificate
- "integrity check failed" / signature errors — your signing certificate may have expired or the partner holds the wrong one.
- "decryption failed" — your encryption certificate mismatched; the partner encrypted to an old or wrong key. See the decryption-failed guide.
Confirm the certificate first
Before digging into MDN internals, rule out the obvious: paste the certificate into the inspector below and check it hasn't expired and matches the fingerprint your partner has.
try it
Paste a certificate
public certificate — PEM or DER, never uploaded
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