DNS Lookup

A maps a name to an IPv4 address, AAAA to IPv6 — these are 'where does this domain point.' CNAME aliases one name to another (www often CNAMEs to the bare domain). MX lists mail servers with priority numbers, lower tried first — 'where does email for this domain go.' TXT holds arbitrary strings, which in practice means email authentication (SPF, DKIM, DMARC) and domain-ownership verification. NS names the authoritative nameservers — 'who answers for this domain.'

Caching, governed by TTL. Nothing in DNS is pushed; resolvers cache each answer for its TTL (shown per record here) and only re-ask when it expires — so a record with a 3600s TTL can legitimately show its old value for up to an hour after you change it, longer if intermediate caches are sloppy. The pro move for planned changes: lower the TTL to 300s a day in advance, make the change, then raise it back. 'Propagation' is just caches expiring at different moments.

Three queries. MX shows where mail is delivered — no MX records generally means the domain can't receive email. TXT reveals the authentication policy: look for a record starting 'v=spf1' (which servers may send as this domain), and a '_dmarc' policy governs what happens to failures (querying _dmarc.domain.com directly works here too). If a domain's mail is landing in spam, missing or misconfigured SPF/DKIM/DMARC in those TXT records is the first place to look.

Because DNS answers can legitimately vary by who's asking. This tool queries Cloudflare's 1.1.1.1; your machine uses your ISP's resolver (or whatever you've configured), and each caches independently — so mid-propagation they'll disagree. Beyond caching, many CDNs return different IPs by geography or load-balance across a pool, so two 'correct' answers can differ. If the records here look right but your machine misbehaves, flushing your local DNS cache is the next step.