DMARC Record Checker reads the DMARC policy published at _dmarc on a domain and explains what it actually does. DMARC ties SPF and DKIM together by adding two things neither has on its own: alignment, which requires the authenticated domain to match the address a recipient sees, and a published policy telling receivers what to do when a message fails. The tool parses each tag and flags the problems that make a record look protective while doing nothing. The most common by far is p=none, which is a monitoring mode: it asks for reports but instructs receivers to deliver failing mail normally. Many domains publish it as a first step and never move on, which leaves them no better protected than before. A missing rua address is the other frequent gap, since without it you receive no aggregate reports and have no way to see what is failing before tightening the policy. A pct value below 100 applies the policy to only a fraction of mail. Check this together with SPF Record Checker and DKIM Record Lookup, because DMARC only passes when at least one of them passes and aligns.
DNS resolution happens in multiple stages. When you type a domain name, your browser first checks its own cache, then the OS resolver cache, then queries your configured DNS resolver (usually your ISP or a public resolver like 8.8.8.8 or 1.1.1.1). If none have the record cached, the resolver performs a recursive query: it asks the root name servers for the TLD servers (.com, .net, etc.), then asks the TLD servers for the authoritative name servers of the specific domain, and finally asks the authoritative servers for the actual record. This entire process typically completes in under 100ms. DNS-over-HTTPS (DoH) encrypts DNS queries in HTTPS traffic, preventing ISPs and network observers from seeing which domains you query. It was standardized in RFC 8484 in 2018 and is now supported by all major browsers. Google and Cloudflare both operate free public DoH endpoints (dns.google and cloudflare-dns.com). TXT records have become a critical security mechanism: SPF (Sender Policy Framework) records specify which servers are allowed to send email for a domain, DKIM (DomainKeys Identified Mail) records provide public keys for verifying email signatures, and DMARC records tell receiving mail servers what to do when SPF or DKIM checks fail. Checking these records is the first step in diagnosing email deliverability problems.