Why Emails Land in Spam Despite Valid SPF, DKIM, and DMARC Records

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Emails can still be filtered as spam even when SPF, DKIM, and DMARC DNS checks return green, because inbox placement depends on domain alignment, not just authentication success. DMARC requires that the domain in the visible From header matches the domain authenticated by either SPF or DKIM, a relationship defined in RFC 7489 as either relaxed or strict alignment. A common misconfiguration occurs when a platform signs outgoing mail with its own shared DKIM domain while displaying a seller's or custom From address, leaving no aligned identifier for DMARC to validate. Developers are advised to inspect the raw delivered message's Authentication-Results header rather than relying on DNS dashboards, and to log immutable delivery evidence including envelope sender, header From, and DKIM values for each outbound message. Beyond authentication, receivers also weigh factors such as complaint history, sending volume patterns, and infrastructure consistency, meaning a passing DMARC result does not guarantee inbox delivery.

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