DNS, email authentication, certificates and passwords. The jobs that come up every week when you look after sites for other people, and the ones that fail quietly when nobody's watching.
Try it — put a domain in and see
Registration, DNS, mail authentication and certificates in one pass. For the full version including security headers and hosting, put a domain in the box above.
Real entropy, shown in bits and years.
Paste raw email headers. See why it went to spam and where it sat waiting.
AnalyseSix public resolvers, asked at once. Disagreement means a stale cache somewhere.
Check a recordEvery hop, with codes and timings. Catches the 302 that should have been a 301.
Trace a URLResolves the whole include chain and counts it against the ten lookup limit — the one that fails silently and takes your mail with it.
Builds both records. DMARC to RFC 9989 with a staged rollout, and SPF with a live count of the lookups your senders actually cost.
Who owns an address, who announces it, and whether its reverse DNS actually confirms.
Look one upCheck what a site sends, then copy the nginx, Apache or WordPress config that fixes what's missing.
Check a siteI build and look after websites for other people. These are the checks I was doing anyway, usually across four browser tabs and a terminal window, usually at the point something had already gone wrong.
So they're built the way I'd want them: no sign-up wall, no upsell, and an answer that says what to actually do rather than just going red.