Domain health guides

Practical explanations for DNS, SSL, HTTP security headers, and email-authentication decisions.

Guides

Understand DMARC p=none, p=quarantine and p=reject, how they differ, and how to move toward enforcement safely.

Learn how to investigate a missing SPF record, identify legitimate senders, and publish one safe SPF policy for your domain.

Understand what a DKIM selector is, where to find it, and how to validate one selector-specific DKIM DNS record safely.

Troubleshoot DNS resolution failures by separating NXDOMAIN, SERVFAIL, delegation and propagation issues before changing records.

Use a practical SSL certificate expiry checklist to review HTTPS reachability, certificate renewal ownership, DNS and post-change verification.

Learn what Content-Security-Policy, Strict-Transport-Security and X-Frame-Options do, and why header presence alone is not a security guarantee.

Use this domain monitoring checklist to review DNS, SSL, HTTPS, email authentication and configuration changes with clear ownership and follow-up.

Understand how SPF, DKIM and DMARC work together, what each public DNS signal means, and how to prioritize email-authentication remediation.