Why can we not find bounce reply, NDR?

When the recipient sends a Non Delivery Report, NDR they may well not include a reference to the original sent object. Additionally the NDR may be sent to Postmaster versus the original sender.

In-reply-to is not a required value for bounced messages, there is no standard that is adhered to for bounced messages. Each provider is unique and it can be Null.

You would need to monitor inbound emails for NDR's.

Resources:

Can you please let us know why this email bounced?

Updated November 24, 2023 09:09