Emails Bouncing

Question

My emails are not sending and keep bouncing for both internal and external contacts. This is the message I receive 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."

Answer 1

Hi Jack,

Thank you for sharing the error message. 

This notification typically means that Microsoft 365 has temporarily restricted the account from sending email because it detected suspicious or unusual outbound activity. This is why messages to both internal and external recipients are being returned.  

If you can still access your account, please change your password to a new and unique password: 

1. Go to https://myaccount.microsoft.com/ 
2. Select Change password 
3. Follow the prompts to update your password 

After changing your password, please contact your organization’s IT administrator. They will need to review the account for any signs of compromise and check whether it has been added to the Email & collaboration > Review > Restricted entities list in the Microsoft Defender portal. Once the account has been secured, the administrator can take the appropriate steps to remove the sending restriction. 

• In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support  

I hope this information is helpful. Should you have any further questions or need additional assistance, please feel free to share them in the comment below. I'm very happy to help. 

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