Microsoft's Rejection Phase Is Live: A 550 5.7.515 Field Guide
Outlook now hard-rejects non-compliant bulk mail with 550 5.7.515, and Safe Senders cannot override it. Diagnosing the bounce and fixing the authentication behind it.
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Outlook now hard-rejects non-compliant bulk mail with 550 5.7.515, and Safe Senders cannot override it. Diagnosing the bounce and fixing the authentication behind it.