Check a domain its mail, DNS and web posture, each record quoted
SPF, DMARC and DKIM say whether forged mail from the domain is refused; MTA-STS and TLS-RPT whether mail to it travels encrypted; DNSSEC and CAA who may answer for it and certify it; HSTS, the security headers, the certificate and security.txt what the front page binds a browser to and whom to tell about a flaw. Lookups only, from this server; nothing is sent to the domain beyond a GET of its front page.
Type a domain. The check reads it by DNS and HTTPS alone — the way internet.nl, Hardenize and MXToolbox do — and quotes every record beside its verdict.