Build Series Vol. 10 — Email & Domain Defense

Domain authentication all the way to enforcement, transport security, portfolio hygiene, and the monitoring that tells you when someone is impersonating you.

The decision this volume is really about: crossing from monitoring to enforcement without breaking legitimate mail.

Control mapping first. The exact SOC 2, ISO 27001:2022, NIST CSF 2.0, CIS v8.1, CMMC, PCI DSS v4.0.1 and HIPAA clauses this build satisfies are printed before any installation step, so the work becomes audit evidence rather than a side effect of it.

A validation harness, not just a build. How to prove the control works and — the part nothing free covers — how to catch it failing quietly: the expired scan credential, the canary that stopped, the encryption key nobody can recover, the segmentation your diagram claims and your firewall does not.

Three sized architectures with honest hour counts. Tier 1 is 20–35 hrs to build · 2–4 hrs a month.

Stack: parsedmarc · checkdmarc · dnstwist · MTA-STS · certificate transparency.

Current as of August 2026. DMARC became an IETF Proposed Standard in May 2026 as RFC 9989, and the pct tag is gone — the protocol's only staged-rollout mechanism. Rollout is now process discipline, and every guide written before May still tells you to ramp with pct.

Every volume runs the same nine sections: prerequisites, control mapping, the decisions that matter, three sized architectures, a build runbook, a validation harness, an evidence pack, an operating cadence with honest hour counts, failure modes and the buy line, and an AI prompt pack.

Reading order: read 6th of ten. Each volume stands alone, and each is cheaper to build if the one before it exists.

Ships without support. This is a document, not a service contract — and Section 8 tells you plainly where the buy line is.