How to handle Microsoft treating DMARC reject policy as quarantine?

Microsoft's approach to DMARC involves treating 'reject' policies as 'quarantine' to prevent false negatives, prioritizing the delivery of legitimate emails even if they fail authentication checks. DMARC policies are viewed as requests, not commands, leaving the ultimate decision on email handling to the recipient server. Microsoft's O365 platform is known to send unaligned emails directly to the spam folder. Recommendations for handling this include monitoring DMARC reports, ensuring proper SPF/DKIM alignment, and considering an Exchange rule to enforce 'reject' policies. Furthermore, senders should be aware of how Microsoft's authentication changes impact forwarded emails and understand that Microsoft often has unique ways of doing things.

Microsoft often treats DMARC reject policies as quarantine to avoid blocking legitimate emails due to misconfigurations or other issues. This is because Microsoft prioritizes avoiding false negatives (missing valid emails). To address this, it's essential to monitor DMARC reports, ensure proper SPF and DKIM setup for alignment, and consider creating an Exchange rule to reject failing emails. It's also important to advocate for alignment with clients, but be aware of Microsoft's abrupt changes to authentication procedures, and how this all affects forwarded emails.

Microsoft's handling of DMARC reject policies as quarantine stems from their unique approach to authentication and the need to balance security with preventing false positives. DMARC policies are essentially requests, not commands, and receivers like Microsoft have discretion. Key elements include the importance of authentication alignment, the limited value of DMARC in many situations, and the fact that Microsoft often moves unaligned emails directly to spam within its Office 365 platform. Senders should understand Microsoft's practices, especially how it affects forwarded emails, and be aware that this forces workarounds.

Microsoft 365 quarantines messages failing DMARC, even with a 'reject' policy, to avoid blocking legitimate emails due to potential misconfigurations. DMARC policies are requests, not commands, giving recipient servers like Microsoft discretion over handling failed authentication. Microsoft routes unaligned mail directly to the spam folder. Ultimately, recipient servers have the final say in how emails failing authentication are handled.