Request for Delisting – IP Blocked by Microsoft (S3150)

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Request for Delisting – IP Blocked by Microsoft (S3150)

DURMUŞ YENİCİ 0

Dear Microsoft Support Team,

We are experiencing an issue delivering emails to Microsoft-hosted domains such as Hotmail and Outlook.

Our mail server IP address: [Moderator note: personal info removed]

When attempting to send emails, we receive the following error: 550 5.7.1 Unfortunately, messages from our IP were not sent. Please contact your Internet service provider since part of their network is on your block list (S3150).

We would like to inform you that:

Our mail server is properly configured and fully compliant with email standards.
SPF, DKIM, and DMARC records are correctly configured and validated.
Reverse DNS (PTR) and HELO/EHLO configurations are correctly set and consistent.
Our server is not listed in any public blacklists.
We actively monitor our systems, and there is no evidence of spam or malicious activity.
DCIM and VSS records/logs indicate that the system is operating normally without any anomalies.

Despite this, emails sent to Microsoft domains (Hotmail, Outlook, Live) are being rejected.

We kindly request a review of our IP address and removal from your internal block list if applicable.

Please let us know if any additional information is required.

Thank you for your assistance.

Best regards,

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Answer 1

Please note that Q&A forum is a public platform, and moderators will modify the question to hide 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.

Please note that this is the Turkish (tr-tr) forum. I kindly recommend posting your question in Turkish so that more community members can assist you effectively. If you prefer using English, you are welcome to post in the English forum instead. I sincerely appreciate your understanding and cooperation.

Hi @DURMUŞ YENİCİ

Having your properly configured mail server blocked from delivering emails to Microsoft domains is incredibly frustrating, especially when you have already ensured that your SPF, DKIM, DMARC, and reverse DNS are perfectly set up. I completely understand that you are receiving the "550 5.7.1 S3150" error stating your IP is on a block list, despite your server having a clean reputation and no evidence of malicious activity.

Please note that as a forum moderator, I cannot manually unblock IP addresses or make changes to internal filtering systems on your behalf. Our role is limited to providing technical guidance to help you navigate the correct support channels.

To get this resolved, have you already tried submitting a delisting request through the official Outlook.com Deliverability Support portal? You can do so here: https://olcsupport.office.com/

If you have already contacted them and received an automated response stating that your IP or domain is not blocked (yet your emails are still bouncing), we highly recommend replying directly to that automated response.

Replying to the auto-responder actively escalates the case to a human support agent. You can see examples of users successfully escalating and resolving their cases this way in the following Microsoft Q&A thread:

How to fix mail delivery error?

Additionally, Microsoft's official guidance states that if you are still experiencing issues after escalating, you should continue submitting tickets to ensure the deliverability team fully investigates your IP's standing.

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I hope this information is helpful and that the backend team can clear up this block for you quickly!

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