Issue receiving with AS2: Invalid S/MIME part format error

Question

While setting up the partner, they tried to send a test file through using AS2. However, the MDN fails and I get the "Invalid S/MIME part format" in the JSON file created. I had the partner send the test file as a text file as a test and the same issue is reported. I also checked the serial number and the thumbprint of the certificate matches to confirm that the correct certificate is imported in. What's strange is that I have no issue sending to them. Is there anything else that could be the issue?

Answer

This error message typically indicates that the AS2 message received by the AWS Transfer Family server is not properly formatted SMIME. Improper SMIME format could be an issue with your trading partner's client. It is also possible there is an interoperability issue between your partner's AS2 server and AWS Transfer Family AS2, but with limited details, we cannot be certain. If you have the option, opening a support case with AWS will allow us to go deeper into your specific issue.

Issue receiving with AS2: Invalid S/MIME part format error

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