Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-20T15:28:50+00:00	DMARC	—	ABSENT	`b7d77c92cfdd…`
2026-08-20T15:28:50+00:00	SPF	—	VALID	`876c427fe12b…`