An overview of SPF, DKIM, and DMARC — the three standards that prove your email is legitimate.
⚡ Monitored by EmailExacto IntelligenceEmail authentication is a set of technical standards that let receiving mail servers verify email claiming to be from your domain actually came from you. The three core standards — SPF, DKIM, and DMARC — work together to prove sender identity, protect message integrity, and enforce what happens when verification fails.
Without authentication, anyone can forge email from your domain. Authentication closes that door and signals to receiving servers that your email is legitimate.
SPF validates the sending server's IP against a DNS allowlist. DKIM cryptographically signs the message content and headers. DMARC ties SPF and DKIM together — requiring one to align with the From: domain — and lets you define what receivers do when neither passes.
For DMARC to pass, either SPF or DKIM must pass and align. Alignment means the authenticated domain matches the From: header. This prevents attackers from passing SPF on a different domain while spoofing your From: address.
Gmail, Yahoo, and Microsoft now require DMARC records for bulk senders. Authentication directly improves inbox placement — authenticated email is trusted, unauthenticated email is suspicious. ISPs use it as a foundational signal in spam classification.
Authentication also enables BIMI — displaying your brand logo in the inbox — which requires DMARC at p=quarantine or higher.
EmailExacto monitors all three authentication records daily and scores them as the foundation of your deliverability health.
✓Implement all three: SPF, DKIM, and DMARC — using only one or two leaves gaps.
✓Progress DMARC from p=none to quarantine to reject as you verify all senders are authenticated.
✓Authenticate every sending source — ESP, CRM, helpdesk, and transactional provider.
✓Test authentication by checking the Authentication-Results header of a sent test message.
✓Set up a DMARC RUA address to receive aggregate reports.
✓Don't forget subdomains — each that sends email needs its own records.
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