554 5.7.1 - 550 5.7.1 - block list (S3140)
If you're managing a server and encounter bounced emails with the error:
Remote server returned '554 5.7.1 <eur.olc.protection.outlook.com #5.7.1 smtp; 550 5.7.1 Unfortunately, messages from [Affected IP] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140).'
Don’t panic! Here’s a step-by-step guide based on my experience to resolve this issue quickly:
Visit Microsoft’s Delist Portal and enter your affected IP address. After submitting, wait for about 30 minutes to see if the block is removed. If not, proceed to the next step.
Email the Outlook Deliverability Support Team at delist@microsoft.com. In your email, include the affected IP address and a detailed description of the issue.
If you're directed to Microsoft’s Online Support Form, complete it and wait for their response. Their email will usually request additional details:
Respond to their request with the necessary details. In my case, they asked for:
If Microsoft requests confirmation in a specific format, contact your ISP and request an email like this:
“The IP [affected IP] was assigned to [Your Name] on [DD/MM/YYYY].”
Once you receive it, forward this document to the Microsoft support team.
After submitting the requested documentation, Microsoft confirmed they implemented mitigation for my IP. They informed me this change might take 24-48 hours to replicate throughout their system.
In under 24 hours, my server was successfully removed from Outlook's block list, and emails were being delivered without issues!
By following these steps, you can resolve IP block issues effectively and minimise email delivery interruptions.