MX record lookup
MX records say which servers accept mail for a domain. If there are none, nothing you send can be delivered, no matter how correct the address looks.
Free, no signup, no daily limit. We do not store what you check here.
The null MX trap
RFC 7505 lets a domain publish a single MX record pointing at the root - just a dot - to declare that it accepts no mail at all. It is a deliberate, machine-readable "do not send here". A validator that counts records rather than reading them sees one MX and concludes mail is deliverable. example.com, the domain in nearly every test suite and tutorial, publishes exactly this.
No MX is not always fatal
RFC 5321 allows a sender to fall back to the A record when no MX exists. It is unusual for a serious mail domain, so treat it as a downgrade rather than a rejection - hard-failing here produces false negatives on small business domains that never configured MX properly.
Questions
What does priority mean?
Lower numbers are tried first. Multiple records with different priorities are a failover arrangement.
Does an MX record prove the address works?
No. It proves the domain can receive mail. Whether that specific mailbox exists is a separate question.
Related tools
Free email address validator
Check syntax, DNS, MX records and deliverability signals for any email address. Free, no signup.
DMARC record checker
Check a domain DMARC policy, alignment and reporting setup. Free live DNS lookup, no signup.
SPF record checker
Check a domain SPF record for syntax problems, soft-fail settings and the 10-lookup limit. Free.
When you need more than a free tool
This page answers what can be determined offline and from public DNS. The API adds live carrier and mailbox verification, a calibrated confidence score, and the full evidence trail behind every verdict.
Credits never expire. Inconclusive verdicts are never billed. Cancel in one call. See pricing or read the docs.