Why emails still go to spam even after fixing SPF, DKIM, and DMARC

A developer discovered that passing all email authentication checks — SPF, DKIM, and DMARC — did not prevent a 4,000-recipient campaign from landing in spam folders. The core issue is that authentication only verifies sender identity, not sender trustworthiness; mailbox providers like Gmail also weigh IP and domain reputation separately. A brand-new domain with no sending history is treated as suspicious by default, since most new domains sending high volumes are associated with spam. Inbox placement improves only as recipients engage — opening and clicking — which gradually builds domain reputation over roughly 45 to 60 days. The recommended strategy is to begin by sending exclusively to highly engaged contacts in small, steadily increasing batches, avoiding cold or purchased lists that may contain spam traps capable of permanently damaging a fresh domain.