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Hi, i am getting the undeliverable email notification. How i can resolve it?

Connie Lim 0 Reputation points
2026-03-31T05:01:24.93+00:00

I keep getting the undeliverable email notification, what should i do? The message that i received as below:

This message couldn't be delivered because the sending email address was not recognized as a valid sender. The most common reason for this error is that the email address is, or was, suspected of sending spam. Contact the organization's email admin for help and give them this error message.

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  1. Teddie-D 13,755 Reputation points Microsoft External Staff Moderator
    2026-03-31T05:38:21.0766667+00:00

    Hi @Connie Lim  

    Thank you for posting your question in the Microsoft Q&A forum.  

    As the error message indicates, this is not something you can resolve on your own. You will need to contact your IT administrator within your organization and ask them to unblock your account through the Microsoft Defender portal > Email & collaboration > Review > Restricted entities after verifying the account is not compromised.  

    For reference, please follow the steps in this article: Remove blocked users from the Restricted entities page - Microsoft Defender for Office 365 | Micros… 

    I hope this information is helpful.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. 

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