Email Authentication Fundamentals — assessment

Sample question

A domain publishes v=DMARC1; p=reject; pct=50. What does pct=50 ask a receiver to do with a message that fails DMARC?

• Apply reject to roughly half of failing messages, and treat the rest as the next weaker policy.pct is a ramp: the sampled share gets the published policy and the remainder falls back to quarantine. Because the sampling is per message and per receiver, a single sender fails intermittently rather than cleanly — which is why pct makes problems harder to diagnose than moving p does.
• Reject half of all messages from the domain, whether they fail or not.pct only ever applies to messages that have already failed evaluation. Passing mail is unaffected.
• Apply reject once at least 50% of the domain’s senders are aligned.Receivers have no view of a domain’s sender inventory and no way to compute that. pct is a per-message sampling rate, not a readiness threshold.
• Send aggregate reports covering 50% of observed traffic.Reporting volume is unrelated to pct. Reports cover everything a receiver saw.

Every option carries an explanation, including the wrong ones.