DNS-over-HTTPS (DoH) lets this page query DNS records straight from your browser using Cloudflare's public resolver at 1.1.1.1, over regular HTTPS instead of the traditional unencrypted UDP port 53 — so no network in between can see or tamper with the lookup. The "check everything" option queries A, AAAA, MX, TXT, NS, CNAME, and SOA in one pass, which is a fast way to confirm a domain's hosting and email setup at a glance.
A missing MX record usually means the domain isn't configured to receive email at all, or mail is deliberately routed through a subdomain with its own record — it doesn't necessarily mean the domain is broken.
TXT records hold arbitrary text, most commonly SPF, DKIM, and DMARC strings that tell receiving mail servers which servers are authorized to send email for that domain — key data when verifying an anti-spoofing setup.
DNS records get cached at multiple points — your OS, router, ISP — each with its own TTL, so a fresh DoH query here can show updated records before they've propagated to your local cache.