Authentication

SPF, DKIM, DMARC, transport security, and domain trust.

Sender Policy Framework (SPF)

Publish one bounded SPF policy that authorizes legitimate envelope senders without exceeding DNS lookup limits or permitting the world.

Sign outgoing mail with DKIM using aligned domains, protected private keys, rotating selectors, and canonicalization that survives normal transit.

Publish DMARC, collect reports, align SPF or DKIM with the visible From domain, and move to enforcement only after legitimate flows pass.