s3150 block list removal

Question

s3150 block list removal

Tempa Ofis 5

We are writing to bring to your attention an issue that is severely affecting our business operations. Our organization's email server has been blocked under the error code S3150, preventing us from sending emails to Hotmail, Outlook, and other Microsoft-hosted email accounts. Server IP address will be shared when requested.

We rely on email communication for critical business. Being listed on your blocklist is significantly disrupting our workflow and causing operational difficulties.

We kindly request an immediate review of this situation and the removal of our IP from the blocklist. Please let us know if any further action is required on our end to resolve this issue.

Thank you for your prompt attention to this matter. We appreciate your support.

Best regards,

AJ Maverick 0 Reputation points

2026-01-21T23:02:50.6033333+00:00

I have recieved the same thing and microsoft stated that I had to contact my internet provider. Yet, you just stated that it is due to my email provider. I would never use an xfinity provided email anymore than I would a microsoft one. So, who am I supposed to contact?

1 answer

Your answer

AJ Maverick 0 Reputation points

2026-01-21T23:02:50.6033333+00:00

I have recieved the same thing and microsoft stated that I had to contact my internet provider. Yet, you just stated that it is due to my email provider. I would never use an xfinity provided email anymore than I would a microsoft one. So, who am I supposed to contact?

Answer 1

Hi Tempa,

To set expectations straight, this is a user-to-user support forum. And we cannot control what algorithm the spam filter is using.

The S3150 error code confirms that your server's IP address has been blocked by the automated spam filtering systems for Outlook.com and Hotmail.

The only method to resolve this is for your email administrator to request delisting by following these steps:

Navigate to the Office 365 Anti-Spam IP Delist Portal here: https://sender.office.com/

Follow the on-screen instructions precisely. You must enter the blocked IP address and an email address that received the non-delivery report (NDR).

Submit the form for review.

It is essential that your organization also investigates and resolves the root cause for the block, such as potential spam generation or compromised accounts, to prevent this from happening again.

I hope you find this information useful. If you have any more questions, don't hesitate to reach out. Otherwise, please take a moment to accept the answer. Wishing you good luck!