My mail wont send

Fiona Nugent 0 Reputation points
2026-09-20T11:38:03.8666667+00:00

I cannot send mail. I have this response

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.

Microsoft 365 and Office | Other
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  1. EmilyS726 267.8K Reputation points Independent Advisor
    2026-09-20T12:32:21.56+00:00

    Are you using an organization assigned email address?

    If so you need to contact your organization IT department and have the admin user check for account compromise or/and recent activities. If they believe your account is ok they can unlock it using the following path.

    Microsoft Defender portal > Email & collaboration > Review > Restricted entities > locate the affected account > Unblock

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