Email Authentication – SPF, DKIM, and DMARC

Email Authentication – SPF, DKIM, and DMARC
SPF Sender Policy DKIM Signed Keys DMARC Policy+Report ✓ SPF: pass ✓ DKIM: pass ✓ DMARC: pass DELIVERED ✓ Authenticated sender Not spoofed

How SPF, DKIM and DMARC work together to stop email spoofing and protect your domain’s reputation.

Email Authentication: SPF, DKIM and DMARC

SPF, DKIM and DMARC are three DNS-based standards that work together to stop email spoofing and keep attackers from sending phishing mail as your domain.

How Email Spoofing Works (Without Authentication)

WITHOUT SPF/DKIM/DMARC — attacker can send email appearing to be from yourcompany.com.au ATTACKER evil.ru mail server From: ceo@yourco.com RECIPIENT’S MAIL SERVER No way to verify! VICTIM’S INBOX Sees: From: ceo@yourco.com Trusts it — gets scammed

The Three Standards Explained

SPF Sender Policy Framework DNS TXT record listing authorised mail servers Answers: “Is this server allowed to send for my domain?” DKIM DomainKeys Identified Mail Cryptographic signature added to outbound email Answers: “Was this email actually sent by the claimed domain?” DMARC Domain-based Msg Auth Policy: what to do when SPF or DKIM fails none → monitor only quarantine → to junk reject → block entirely
✓ Key Point
SPF + DKIM + DMARC p=reject is the configuration to aim for. DMARC is the part that tells receiving servers what to do when authentication fails. Without it, a failing SPF check may still deliver the email. Start with p=none (monitoring only), analyse the reports, then move to p=quarantine, then p=reject.

DMARC Deployment Stages

Stage DMARC Policy Effect
1. Monitor p=none No blocking. You receive reports on who is sending as your domain
2. Quarantine p=quarantine Failed emails go to spam/junk
3. Enforce p=reject Receiving servers block failed emails, so nobody can spoof your domain
⛔ Important
Many organisations set up SPF and DKIM but leave DMARC at p=none permanently. That gives you visibility but no protection, and a spoofed email claiming to be from your domain still reaches the recipient. Finish the deployment by moving to p=reject once you have verified all legitimate sending sources pass authentication.

Checking Your Domain’s Email Authentication

You can verify your domain’s SPF, DKIM, and DMARC records using free tools like:
  • MXToolbox (mxtoolbox.com) checks all three records
  • DMARC Analyser reviews DMARC aggregate reports
  • Google Admin Toolbox checks deliverability
When checking a received email, look at the email headers for Authentication-Results:, which shows whether SPF, DKIM and DMARC passed or failed.

Mobile Techs IT Consulting

Could a scammer send email as your domain right now?

If your DMARC policy is missing or stuck on p=none, anyone can spoof your domain to scam your customers and suppliers, and your legitimate email may be landing in junk folders too. Mobile Techs IT Service helps Gold Coast businesses get email authentication right: SPF, DKIM, and DMARC configured correctly for every sending service, DMARC reports monitored, and a safe staged move to p=reject that protects your brand without breaking your mail flow. Home users welcome too, on-site or remote, anywhere in Australia.

Get your domain records checked Talk to us first

Call 1300 644 588  ·  office@mobiletechs.com.au
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