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DMARC, DKIM & SPF: The Email Security Trifecta That Determines 30% of Your Security Grade

Nearly 60% of organizations we rate have misconfigured email authentication. Here's what each protocol does, how to check your current setup, and how to fix it without breaking your mail flow.

Brian Kowalski
Email Infrastructure Engineer
Feb 19, 2026 5 min read

Email authentication protocols are the single highest-impact, lowest-effort way to improve your cybersecurity rating. Together, SPF, DKIM, and DMARC prevent your domain from being spoofed in phishing attacks — and their absence is a major red flag for security rating platforms, compliance auditors, and cyber insurers.

The Three Protocols Explained

SPF

Sender Policy Framework

SPF publishes a list of IP addresses authorized to send email from your domain as a DNS TXT record. When receiving mail servers check SPF, they verify the sending IP is on your approved list.

v=spf1 include:_spf.google.com include:sendgrid.net ~all

⚠️ Use "-all" (hard fail) instead of "~all" (soft fail) for maximum protection and scoring benefit.

DKIM

DomainKeys Identified Mail

DKIM adds a cryptographic signature to every outgoing email, allowing receiving servers to verify the message wasn't tampered with in transit. Your mail server signs with a private key; the public key is published in DNS. Use 2048-bit RSA keys minimum — 1024-bit keys are now considered weak and penalized.

DMARC

Domain-based Message Authentication, Reporting & Conformance

DMARC ties SPF and DKIM together and tells receiving servers what to do when a message fails those checks: nothing (p=none), send to spam (p=quarantine), or reject outright (p=reject). Only p=reject provides full protection and maximum scoring credit.

v=DMARC1; p=reject; rua=mailto:[email protected]; pct=100

Implementation Order That Won't Break Your Mail

  1. 1.Start with DMARC p=none to collect reports without affecting mail flow. Monitor for 2–4 weeks.
  2. 2.Identify all legitimate sending sources from your DMARC reports. Update your SPF record to include all of them.
  3. 3.Configure DKIM signing on every mail platform you use (Google Workspace, Microsoft 365, SendGrid, Mailchimp, etc.).
  4. 4.Move DMARC to p=quarantine at pct=25%, then 50%, 100% over 4–6 weeks while monitoring reports.
  5. 5.Move to p=reject once you're confident all legitimate mail passes authentication.

Check Your Email Security Score Now

Get a free report showing your DMARC, DKIM, and SPF status — plus everything else affecting your security grade.

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