Hotmail is blocking O365 Servers

Hi @Root777

Thank you for your patience and for sharing the details about the issue you’re facing when sending emails from Microsoft 365 GCC to Hotmail addresses. The error message suggests that the sending IP address is currently blocked by Outlook.com due to reputation or policy reasons. 

To help you resolve this as smoothly as possible, here are some steps you can follow: 

Check SPF, DKIM, and DMARC Configuration 

Please ensure your domain has valid SPF, DKIM, and DMARC records properly configured and aligned with your sending setup. 

• SPF: For Microsoft 365, the recommended SPF record is v=spf1 include:spf.protection.outlook.com -all 
• If you're using a third-party service or on-premises relay, make sure the SPF record also includes the appropriate ip4: entries for those IP addresses. 
• DKIM: Confirm that your outgoing messages are signed with a valid DKIM. 
• DMARC: Check that your DMARC policy is configured correctly. At a minimum, setting it to p=none allows you to monitor authentication without affecting delivery. 

Review Sending Infrastructure  

Please check whether your email traffic is being routed through any on-premises servers or third-party relays. In such cases, the IP address evaluated by Outlook.com may not be part of Microsoft's standard outbound IP pool. 

Submit a Delisting Request via Microsoft Sender Support 

If the IP address is still blocked, you can request delisting through Microsoft’s Sender Support portal: https://sender.office.com 

When submitting the request, please include: 

• The blocked IP address
• The full Non-Delivery Report (NDR) or message headers showing the rejection 
• Confirmation that the IP is not listed on any public blocklists 
• A brief explanation of any corrective actions you've taken to improve your sender reputation 

After submitting the form, be sure to complete the email verification step to finalize the process. 

Please allow up to 48 hours for the request to be processed. If the issue persists beyond that, I recommend reaching out to your mail provider or contacting Microsoft 365 Support via the Admin Center for further assistance. 

If you'd like me to help review your setup or go through any part of the process together, just let me know. I'm more than happy to assist. 

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