Fix "Outlook S3140 / S3150": Your IP was blocked by Outlook's filtering (S3140/S3150)

If your email is bouncing with Outlook S3140 / S3150, it means your IP was blocked by Outlook's filtering (S3140/S3150). Here is exactly what causes it and how to fix it.

What Outlook S3140 / S3150 means

These Microsoft codes mean your IP has been blocked or heavily filtered due to reputation. Outlook is notoriously conservative with new or shared IPs.

How to fix Outlook S3140 / S3150

• Request delisting via the Microsoft sender support form.
• Move to a dedicated IP with clean reputation and warm it up.
• Keep complaint rates extremely low for Outlook audiences.

How Rainmail helps

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