Emails blocked by Outlook.com with NDR error 550 5.7.515 despite correct SPF/DKIM/DMARC records

Question

Hello Microsoft Team,

Our company is currently experiencing an issue where emails sent to Outlook.com / Microsoft consumer accounts are being rejected with the following NDR error:

"550 5.7.515 Access denied, sending domain does not meet the required authentication level."

Our IT department has double-checked our DNS settings and confirmed that our SPF, DKIM, and DMARC records are all correctly published and fully aligned. The configuration has been in place for more than 48 hours, but our emails are still being blocked.

Could you please open a Private Message channel with me, or provide a secure contact email? I need to share our specific sending IP, sending domain, and the full NDR header for your investigation, which are too sensitive to post publicly on this forum.

Thank you for your help!

Best regards

Willie L.

Answer 1

You can also review other common causes and troubleshooting steps here:

https://substrate.office.com/ip-domain-management-snds/Postmaster/Troubleshooting

If you have met all the requirements and still need assistance, you will need to contact Microsoft's dedicated team by using this form. They do respond but can take 24-48 hours.

http://go.microsoft.com/fwlink/?LinkID=614866