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Fix NDR error "550 5.7.515" in Outlook.com

Jean Destine 0 Reputation points
2025-08-19T09:10:31.6+00:00

I am a developer for an e-commerce company that uses the e-commerce platform Magento2. My order confirmation emails for customers who are Microsoft users get bounced with the following error 550 5.7.515 Access denied, sending domain <DOMAIN> doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. I have confirmed the DKIM, DMARC, and SPF configurations with SMTP2GO and Cloudfarre, which seem correct. I also used DNS lookup sites to look up the domain, which indicates that everything is fine. I contacted SMTP2GO's customer service, and everything seems fine to them.
We have various email templates sent to customers; only the order confirmation emails bounce.
Can anyone help me resolve this issue?

Outlook | Web | Outlook on the web for business | Email
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  1. Tamara-Hu 1,950 Reputation points Microsoft External Staff Moderator
    2025-08-19T11:47:47.57+00:00

    Hello @Jean Destine, 

    Thank you for posting your valuable question on Microsoft Q&A forum. 

    The "550 5.7.515" error indicates that Microsoft rejected your email because it didn't pass authentication checks. It's part of Microsoft's effort to enforce strong email authentication to reduce phishing and spam. 

    Microsoft has released an official article about this issue, you can learn more about it at Fix NDR error "550 5.7.515" in Outlook.com - Microsoft Support 

    If you've tried all the steps provided but still couldn't resolved your issue, please kindly contact Microsoft Support Team for deeper analysis.    

    May I ask if you're currently using a Microsoft tenant or account? If not, please kindly contact your partners who are using Microsoft service to see if they can request a support ticket on your behalf.   

    To contact Microsoft support for Personal accounts (hotmail, gmail, yahoo,…): 

    1. Go to https://support.microsoft.com/contactus   
    2. Choose Office > Get home support  

     User's image

    1. Enter Office or your issue in general in the box below "We're here for you" then click "Get Help.
    2. Scroll down and click on Contact Support then log in to your personal Microsoft account  

    If the account cannot be logged in, you can use another account or create a new account to execute.

    1. Select "Microsoft 365 and Office" in Products & Services, select "Technical Support" as a category, and click Confirm.
    2. Select "Chat in a web browser and support specialist" to enter the chat window.

    To contact Microsoft support for Business/Education accounts (usually with a company or school name), please refer to Get support - Microsoft 365 admin.  If you’re unsure who the Microsoft 365 Admin is within your organization, you can find guidance on locating them here: How do I find my Microsoft 365 admin? - Microsoft Support.   

    Apologies for redirecting you to the related development team support as the moderators in this forum have limited resources to check the backend information, and to get the fast and better assistance we requested for it.  Thank you for your cooperation and understanding!

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". 

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. User's image

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