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Interview question · Network Security & Protocols

How do SPF, DKIM and DMARC work together to stop email spoofing, and what do they not stop?

SPF checks a server, DKIM checks a signature, and neither checks the From line the user reads. DMARC ties them to that line. Interviewers want the alignment idea, then the phishing that still gets through.

mediumNewPreparation tags: Google, Microsoft, AmazonUpdated Nov 2026

SPF checks a server, DKIM checks a signature, and neither checks the From line the user reads. DMARC ties them to that line. Interviewers want the alignment idea, then the phishing that still gets through.

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What would you say before reading the answer?

  1. 01 State the assumptions your answer depends on.
  2. 02 Explain the mechanism and choose a control.
  3. 03 Name a condition that would change your decision.

The worked answer includes an approach, scoring criteria and follow-up questions. Compare the reasoning with your own.

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What if · the follow-ups in this answer

The answer works through 6 follow-ups like an interviewer would

Attackers send phishing emails that appear to come from your company's domain to customers and partners.

  1. What does SPF do?
  2. What does DKIM do?
  3. What does DMARC add?
  4. How do you reach enforcement safely?
  5. What does DMARC not stop?
  6. What would you implement?

Each rung has a nudge, a model answer, the principle that carries over and the weak answer to avoid. Premium opens every answer and ladder.

UP NEXT ON YOUR JOURNEY
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