S3150 blocklist please

Question

Hello. My company's email server (93.93.129.152) has been placed on a blocklist, so none of our hotmail/outlook customers can receive emails from us. We issue a twice-weekly jobsletter and perhaps this has been mistaken for spam? But it is voluntary subscription, highly focused, has a prominent Unsubscribe button and completely compliant with EU GDPR and general best practice. Any tips on how to be taken off the S3150 blocklist please?

Answer 1

Hello Clare Bradbury,

Thank you for reaching out to the Microsoft Q&A forum. I understand how confusing and overwhelming this situation can be, especially when you’ve already tried multiple suggestions without success.

Please note that as a forum moderator, I’m unable to directly remove blocks or make changes on your behalf. Since you’ve already attempted the standard troubleshooting steps, the recommended next action is to escalate the issue for a manual review by the Outlook Deliverability Support Team using the following link: https://olcsupport.office.com/

When submitting the request, please include:

• Issue Title: "IP blocked with error S3150 - Mitigation Request"
• IP Address: Your IP address
• Error Message: Paste the full “550 5.7.1 … (S3150)” error log

Providing complete and accurate information will help the team review your case more efficiently.

I hope this helps move your case forward. If you have any additional questions, please feel free to reply in the thread.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".   

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Please can I have a non-AI answer?

Answer 3

Hello.

With reference to

Contact Microsoft Support: If the delist portal does not resolve the issue, you may need to ask a Microsoft 365 recipient to open a support ticket on your behalf, as external senders typically cannot open support tickets directly.

yes please - perhaps someone could help? Please could someone open a support ticket for us? I've followed the suggestions in 1 and 2 but nothing happens and I feel as if I'm just talking to AI and regarding 4 and 5 we're are continually endeavouring to improve our best practice. We are a small business and our emails are highly focused and relevant. We don't send out spam and there is a bespoke Unsubscribe button on every jobsletter email - we try to follow EU GDPR and general best practice with all of our operations.

WE wold take any advice given to us regarding why we may have been placed on a Blocklist. We are parsing all our bounces looking for reasons and then purging any expired email addresses etc. Our Users are reliant on our services and many have hotmail or outlook addresses. Anything you can help us with would be invaluable please

Answer 4

If your email server (93.93.129.152) is on a blocklist, you can take the following steps to request removal:

1. Use the Office 365 Anti-Spam IP Delist Portal: Go to the Office 365 Anti-Spam IP Delist Portal to request removal from the blocked senders list. You will need to provide the email address that received the non-delivery report (NDR) and the IP address specified in the error message.
2. Follow Instructions in Non-Delivery Reports (NDRs): If you receive an NDR, it typically contains instructions on how to proceed. Make sure to follow those instructions closely.
3. Contact Microsoft Support: If the delist portal does not resolve the issue, you may need to ask a Microsoft 365 recipient to open a support ticket on your behalf, as external senders typically cannot open support tickets directly.
4. Review Best Practices: Ensure that your email practices comply with best practices for email deliverability, including proper authentication and avoiding spam-like characteristics in your emails.
5. Monitor Your Sender Reputation: Regularly check your sender reputation and take steps to maintain it, as a poor reputation can lead to being placed on blocklists.

If your emails are compliant with regulations and best practices, following these steps should help you get delisted from the blocklist.

---

References:

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