Emails Bouncing

Jack Duffy 0 Reputation points
2026-09-08T19:56:21.27+00:00

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."

Outlook | Windows | New Outlook for Windows | For business

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  2. Chris-D 2,625 Reputation points Independent Advisor
    2026-09-08T20:28:41.7833333+00:00

    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.

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