What is a mx record?
Also called: mail exchange record
An MX record is a DNS entry naming the mail servers that accept email for a domain, each with a priority number where lower is tried first. A domain with no MX record cannot receive email at all, which makes the MX lookup the fastest way to eliminate a large share of invalid addresses.
MX records are the second step of verification, after syntax. Google Workspace domains point at aspmx.l.google.com, Microsoft 365 at *.mail.protection.outlook.com, and the pattern reveals the mail provider — which in turn tells a verifier how that provider tends to answer mailbox probes.
A missing MX record is usually a typo in the domain rather than a domain with no mail. That is why a no-MX result is the right place to suggest the nearest well-known provider: gmial.com has no mail server, and the useful answer is 'did you mean gmail.com?' rather than simply 'invalid'.
Last reviewed 2026-09-11