Can't send emails

Question

Can't send emails

Shannon 0

I can't send emails. Keep getting this message "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."

Ryan-N 14,420 Reputation points Microsoft External Staff Moderator

2026-08-01T20:37:46.8166667+00:00

Hi Shannon,

I hope everything is going well on your end.

I’m following up on the support thread we've been working through together. I wanted to check in and see if the information I shared in my previous answer helped resolve the issue you were experiencing.

If you're still experiencing any issues or have further questions, please feel free to reach out at any time. I’m always happy to help if you need anything else.

I want to ensure everything is functioning smoothly and that your experience remains seamless.

Thank you again for your collaboration throughout the troubleshooting process. I look forward to hearing from you soon.

Warm regards,

1 answer

Your answer

Ryan-N 14,420 Reputation points Microsoft External Staff Moderator

2026-08-01T20:37:46.8166667+00:00

Hi Shannon,

I hope everything is going well on your end.

I’m following up on the support thread we've been working through together. I wanted to check in and see if the information I shared in my previous answer helped resolve the issue you were experiencing.

If you're still experiencing any issues or have further questions, please feel free to reach out at any time. I’m always happy to help if you need anything else.

I want to ensure everything is functioning smoothly and that your experience remains seamless.

Thank you again for your collaboration throughout the troubleshooting process. I look forward to hearing from you soon.

Warm regards,

Answer 1

Hi Shannon,

Welcome to the Microsoft Q&A forum.

Based on the error message you provided, your email address may have been marked as a Bad Outbound Sender because it sent too many emails within a short period of time. In this situation, the system may identify the account as a potential source of spam and block it from sending outbound emails in order to protect the tenant's data and security.

In this case, you will need to contact your administrator (for example, your organization's IT department) and ask them to remove the restriction from your account.

If you are an administrator, please follow the steps below to unblock the account:

Go to Microsoft Defender Portal.
Navigate to:
- Email & collaboration
- Review
- Restricted entities
Locate the affected email address.
If the account appears in the Restricted Entities list:
- Select the account.
- Choose Unblock.
- Reset the user's password and enable MFA to improve account security.

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this.

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

I look forward to continuing the conversation.

If the answer is helpful, please click "Yes".

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