Did you check this article to solve the error - https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/mfi-non-delivery-report?view=o365-worldwide
Error: The message was not delivered.

Пүрэвжаргал Ганболд
1
Reputation point
Hi,
My order email has stopped going. how to fix it
error message:
Error: The message was not delivered. A non-delivery report (NDR) message was sent to .....The NDR might provide more details about why the email message wasn't delivered and how to fix the issue.
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Hi @Пүрэвжаргал Ганболд ,
Is there any update?
Would you please get back to me at your earliest convenience? Because your response is of great importance for the following trouble shooting. If you need further help, please provide more detailed information, so that we can give more appropriate suggestions.
Thank you for your understanding.
I look forward to hearing from you.