Website security: headers, CSP, DMARC and hacked sites

This is the thread for questions about website security.

Our Security Audit scoring was built to mirror Mozilla HTTP Observatory, then extended with DNS, SPF, DKIM, DMARC and known CVE checks: {S}/security-audit.html

I have answered the most asked questions on this topic here:
https://aiwebpageseo.com/website-security-answers.html

Which security header or email record are you stuck on? Paste the header or DNS record (remove anything private).

Reply below and I will answer.