DNS tools and email checkers

Which one do you need?

The five overlap on purpose — DNS is one system and these are five questions people ask of it. What separates them is the symptom you arrived with.

A name resolves to the wrong place, or not at all

Start with DNS Lookup. It returns the A, AAAA, CNAME, MX, TXT and nameserver records a resolver can see for a hostname, which is enough to tell a missing record apart from a wrong one. If the record looks right to you and wrong to someone else, the difference is usually time rather than configuration — see the propagation tool below.

You changed a record and only some people see it

DNS Propagation asks several public resolvers the same question at the same moment and shows where their answers disagree. Disagreement is normal for a while after a change: each resolver caches an answer for the record's TTL and will not look again until that expires, so the spread you see is the tail of the old value ageing out.

Inbound mail is not arriving

MX Lookup shows which servers a domain nominates to receive its mail, and in what priority order. A domain with no MX records does not silently fall back to nothing — senders may try the A record instead, which is rarely what anyone intended.

Mail you send is going to spam, or being rejected

That is the other direction, and it is two records rather than one. SPF Checker reads the policy naming which servers may send as your domain; DMARC Checker reads what you have asked receivers to do when a message fails that check — nothing, quarantine, or reject. A strict DMARC policy over an incomplete SPF record is the common way a domain starts rejecting its own mail.

You need to know who a domain is registered with, or when it expires

WHOIS Lookup asks the domain’s registry for its registration record: the registrar, the expiry date, the status codes and the nameservers it delegates to. That last one is the place to look when DNS changes seem to have no effect — if the registry still delegates to an old provider, edits at the new one are never read.

Every lookup here runs live at the moment you press the button — against public DNS, or for WHOIS against the domain’s registry. Nothing is pre-computed, so a result is as current as the server that answered it — and two DNS runs a minute apart can legitimately differ while a change is still spreading.