Cannot send/reply to emails from <Removed PII> to <Removed PII> – 550 bounce error

Question

We are experiencing an issue with our Microsoft 365 business account.

Incoming emails to <Removed PII> are working fine.

When replying or sending emails from <Removed PII>, the messages bounce back with a 550 error.

The bounce message indicates that the mailbox may not exist, is deactivated, or there may be a domain configuration issue (MX/SPF/DKIM).

Emails to other domains from the same account work successfully.

We have tried sending via Outlook Webmail and Outlook Desktop App; the issue persists.

This is a business account and urgent communication is affected.

Kindly advise on the corrective actions to resolve outbound mail flow from<Removed PII>.

Answer 1

Hi @ajaybabu,

Welcome to Microsoft Q&A, and thank you very much for reaching out.

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.

Based on your description, I checked on your domain and found that your domain currently doesn’t return the required DNS record, which can lead to the error 550 you are seeing. I have sent the result through private message, feel free to check it there.

Regarding why the mailbox is still able to receive email, from my research, your MX record is confirmed to be present, and that alone is enough for other mail services to deliver messages to your domain.

Therefore, I strongly recommend you or your admin reviewing the domain DNS configuration again and verifying that your DNS records are correctly set. For more detailed guidance, you can check this Microsoft documentation here.

I hope this helps.

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Answer 2

      This is an automatically generated Delivery Status Notification.     

 

Delivery to the following recipients failed permanently:

 

   * <Removed PII> 

Reason: There was an error while attempting to deliver your message with [Subject: "RE: welcome"] to <Removed PII>. MTA <Removed PII> received this response from the destination host IP - <Removed PII>-The mail server could not deliver mail to <Removed PII>.  The account or 550-domain may not exist, they may be blacklisted, or missing the proper dns

550 entries.

Answer 3

To resolve the issue with the 550 bounce error when sending emails from your <Removed PII> account, you can follow these steps:

1. Check the Mailbox Status: Ensure that the mailbox for <Removed PII> is active and not deactivated. You can verify this in the Microsoft 365 admin center.
2. Verify Domain Configuration: Since the bounce message indicates a potential domain configuration issue, check the following:
   • SPF Record: Ensure that your SPF DNS record is correctly set up for the <Removed PII> domain. This record should include all IP addresses that are allowed to send emails on behalf of your domain.
   • MX Records: Make sure that the MX records for <Removed PII> are correctly configured to point to Microsoft 365.
   • DKIM Configuration: If you are using DKIM, ensure that it is properly set up for your domain.
3. Check for High Risk Delivery Pool: Verify if the outbound messages are being routed through the High Risk Delivery Pool, as messages in this pool may not pass SPF checks. You can configure outbound spam policy notifications to receive alerts for such cases.
4. Test with Different Clients: Since you mentioned trying both Outlook Webmail and the Outlook Desktop App, ensure that the issue persists across different platforms. This can help isolate the problem further.
5. Contact Support: If the issue continues after checking the above configurations, consider reaching out to Microsoft support for further assistance, as they can provide more detailed diagnostics based on your account and settings.

Following these steps should help you identify and resolve the issue with sending emails from your <Removed PII> account.

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References:

• Fix NDR error "550 5.7.23" in Exchange Online
• Email bounce categories