DMARC vs SPF vs DKIM

Understanding the three pillars of email authentication and how they work together to protect your domain.

Quick Answer

You need all three for complete email security:

  • SPF authorizes which servers can send email for your domain
  • DKIM signs your emails to verify they haven't been tampered with
  • DMARC tells receivers what to do when SPF or DKIM fails
FeatureSPFDKIMDMARC
What it doesSpecifies authorized mail serversAdds cryptographic signature to emailsEnforces policy when authentication fails
How it worksChecks sender IP against authorized listVerifies email signature with public keyValidates SPF/DKIM alignment + enforces action
Protects againstSender IP spoofingEmail tampering, replay attacksDomain spoofing, phishing
Setup difficultyEasyMediumEasy
DNS record typeTXTTXT (selector-specific)TXT at _dmarc
Provides reports
Can stand alonePartial protectionPartial protectionNeeds SPF/DKIM

How They Work Together

1

Email is sent

Someone sends an email claiming to be from your domain

2

SPF check

Receiver verifies the sender's IP is authorized in your SPF record

3

DKIM check

Receiver validates the email signature using your public key

4

DMARC evaluation

Receiver checks if SPF/DKIM "From" domains align with the email's "From" domain

5

Policy enforcement

If DMARC fails, receiver applies your policy (none/quarantine/reject)

6

Reporting

Receiver sends you a report about the authentication results

Which Do You Need?

For Basic Protection:

Start with SPF and DMARC in monitoring mode (p=none). This gives you visibility and some protection.

For Strong Protection:

Implement all three: SPF, DKIM, and DMARC with p=quarantine or p=reject. This is the gold standard.

Don't Do This:

Don't implement DMARC p=reject without first testing with p=none. You could block legitimate emails.

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