Outlook e-mails not sending

Question

Outlook is not sending e-mails. This message keeps coming up: 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.

Answer 1

Hi @Jack Burke, 

Thank you for reach out and sharing the error message you encountered when trying to send your emails. According your concern, the error typically occurs if you exceed the outbound sending limits of the service or the limits in outbound spam policies. 

To resolve the issue, I would recommend reaching out to your organization's IT admin and provide them with these steps: 

1. Sign into the Microsoft Defender portal at https://security.microsoft.com, go to Email & collaboration > Review > Restricted entities.  

 

2. On the Restricted entities page, select your user account to unblock by selecting the check box for the entity, and then selecting the Unblock action that appears on the page. 

 

3. In the Unblock user flyout that opens, read the details about the restricted account on the Overview page. When you're finished on the Overview page, select Next. 

  

4. On the Unblock user page, select Submit. 

5. Select Yes in the warning dialog that opens. 

For more information, please refer to this document: Remove blocked users from the Restricted entities page - Microsoft Defender for Office 365 | Microsoft Q&A.

I hope this information is helpful. Please follow the steps above and let me know if it works for you. If not, we can continue working together to resolve the issue.  

Thank you for your patience and understanding. If you have any questions or need additional assistance, please don’t hesitate to reach out so I can continue to support you. If you found the response useful, please consider marking it as accepted, as this may help other community members who are looking for similar guidance.  

I look forward to continuing the conversation. 

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