SPF, DKIM, and DMARC.
Learn what SPF, DKIM, and DMARC means in modern search and SEO.
Three DNS-based email authentication standards that verify a sender's identity and instruct recipient mail servers on handling failures.
SPF, DKIM, and DMARC are complementary email authentication protocols published as DNS records. Together they prevent spammers from sending mail that appears to originate from your domain and improve inbox placement rates for legitimate marketing and transactional email.
How Each Protocol Works
SPF lists the IP addresses authorised to send email from your domain. DKIM attaches a cryptographic signature to outgoing mail that recipients can verify against a public key in DNS. DMARC tells receiving servers what to do (none, quarantine, or reject) if SPF or DKIM checks fail, and provides aggregate reporting on email flows.
Google and Yahoo Sender Requirements
Since February 2024, Google and Yahoo require bulk senders to have SPF and DKIM authentication, a valid DMARC record, and a one-click unsubscribe link in email headers. Senders that fail these requirements face rejection or heavy spam filtering for their campaigns.
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