Microsoft is blocking our emails

Question

Hello,

Microsoft is blocking out emails.

[52.101.68.13] Remote Server returned '554 5.0.0 <[52.101.68.13] #5.0.0 smtp; 5.1.0 - Unknown address error 550-"5.7.1 Unfortunately, messages from [185.152.220.250] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150)

how we can fix this?

Answer 1

Hi @Tangoball76

Thank you for reaching out to the Microsoft Q&A Forum and sharing your issue.

You may want to try the steps below to help resolve this issue:

As mentioned by Q&A Assist, you may submit a delisting request through Microsoft’s sender portal: https://sender.office.com/. Please note that this portal is primarily intended for business/enterprise senders.

If you are instead dealing with consumer email (such as Hotmail.com, Live.com, or Outlook.com), the more appropriate portal would be: https://olcsupport.office.com/

Additionally, the error message recommends contacting your Internet Service Provider or hosting provider, as they may need to investigate the IP/network reputation and escalate the issue with Microsoft if required. Please provide them with the full SMTP rejection details when doing so.

If you are using Microsoft 365 services, you may also submit a support ticket through the Microsoft 365 Admin Center. A Microsoft support agent will be able to assist you directly and provide more information.

For further instructions, you can follow this guide: Get support - Microsoft 365 admin | Microsoft Learn 

You may also find this article useful, as it includes additional suggestions and explanations about Microsoft delisting: https://bentonow.com/posts/microsoft-delisting-s3150-s3140

Note: Microsoft is providing this information as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.

Hope this helps. Please let us know if you have any updates or further questions.

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Answer 2

To resolve the issue of Microsoft blocking your emails, you can follow these steps:

1. Check Block List Status: Verify if your IP address (185.152.220.250) is on a block list. You can use third-party services like MXToolbox to check this.
2. Delist Request: If your IP is indeed on a block list, you can request removal using the Office 365 Anti-Spam IP Delist Portal. Follow the instructions provided there to submit your request.
3. Contact Your ISP: Since the error message suggests contacting your Internet Service Provider (ISP), reach out to them for assistance. They may need to address issues on their end that could be causing your IP to be blocked.
4. Review Email Practices: Ensure that your email sending practices comply with Microsoft’s guidelines to avoid being flagged as spam. This includes proper authentication (SPF, DKIM, DMARC) and avoiding sending unsolicited emails.
5. Monitor for Future Issues: After resolving the current issue, monitor your email sending practices to prevent future blocks. Regularly check your IP status and maintain good sending reputation.

By following these steps, you should be able to address the blocking issue effectively.

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References:

• External senders - Use the delist portal to remove yourself from the blocked senders list and address 5.7.511 Access denied errors
• External senders - Troubleshoot email sent to Microsoft 365