Guides

Reproduce DNSSEC, DANE, mail-authentication, and SMTP transport findings from their evidence sources, trust boundaries, decision rules, and known limits.

How to take a domain from p=none to p=reject in deliberate stages: SPF and DKIM groundwork, report reading, the forwarding problem, and when tightening is actually safe.

Design SPF policies that stay below the 10-lookup ceiling without trading a visible failure for silent authorization drift.

Rotate DKIM keys through observable overlap phases while keeping providers isolated and retiring stale selectors cleanly.

Follow authentication through forwarders and mailing lists, then judge ARC evidence without mistaking chain validity for trust.

Build the full BIMI trust chain from enforced DMARC to a production SVG and evidence that relevant receivers can use.

A working method for header analysis: trusting the right Received lines, reading Authentication-Results without wishful thinking, and following ARC through forwarding hops.

A field-tested sequence for introducing DANE/TLSA on your mail infrastructure: prerequisites, record design, rollover discipline, and the failure modes that actually cost mail.

How the two transport-security mechanisms differ, why serious mail domains publish both, and how TLS-RPT turns silent delivery failures into readable reports.

Design MX routing that survives failure, avoids weak backup paths, and supports provider migration without losing queued mail.

Audit receiving mail infrastructure from MX discovery through authenticated TLS, policy enforcement, and reverse identity.

Turn TLS-RPT aggregates into operational evidence by preserving policy, route, volume, reporter, and time context.

Build effective browser security policy across CSP, HSTS, cookies, isolation, redirects, and layered infrastructure.

Turn a valid security.txt file into a disclosure process that can receive, triage, remediate, and close real vulnerability reports.

Reduce TLS attack surface with measured compatibility, deliberate cipher and resumption policy, and expiring legacy exceptions.

A diagnostic method for TLS incidents when all you have is the client's view: name mismatches, SNI surprises, chain problems, protocol downgrades, and the header layer above the handshake.

What CAA does and does not control, how CAs actually evaluate the records, ACME account pinning with RFC 8657, and the renewal failures teams inflict on themselves.

Why DNSSEC failures look like partial outages, how to classify secure, insecure, and bogus states fast, and the two root causes behind almost every real incident.

Understand how NAT, CGNAT, dual stack, and forwarded headers shape the address a service sees and the policies you can safely build on it.

Build a scalable IPv6 address plan around /64 links, readable prefix hierarchy, route aggregation, deliberate reserves, and authoritative documentation.

Treat redirects, canonicals, robots rules, hreflang, sitemaps, and internal links as one system and remove the contradictions crawlers must otherwise resolve.

A practical tour of the emerging agent-facing metadata layer — crawler policy for AI user agents, llms.txt navigation, A2A agent cards, and WebMCP tool exposure — and how to publish it without faking what you do not have.

Use llms.txt as a curated reading map, keep it consistent with access and indexing signals, and validate both draft and deployed file.

Expose website functions as precise WebMCP contracts with UI parity, explicit side effects, runtime checks, and a clear A2A boundary.

Trace EDID through real HDMI chains, isolate capability loss hop by hop, and use emulation without mistaking it for a bandwidth fix.