MX Record Checker
Check a domain's mail routing
See exactly where a domain's mail is routed: every MX record with its priority, the addresses each one resolves to, and the reverse DNS on those addresses. The common configuration faults are called out too — an MX pointing at a CNAME, an MX pointing at an IP address, a hostname that does not resolve, or no mail routing at all.
Frequently asked questions
What does the MX priority mean?
Lower numbers are tried first. A sender attempts the lowest-priority host, and only falls back to higher numbers if it cannot connect. Equal priorities are chosen at random, which spreads load rather than providing failover.
Can an MX record point at a CNAME?
It should not. RFC 2181 requires an MX to name a host with an address record. Many senders tolerate a CNAME, some do not, and the ones that do not simply fail to deliver — which is a miserable problem to diagnose.
Why does reverse DNS matter?
It matters for the address that sends mail rather than the one that receives it, but on a small setup they are the same machine. A sending IP with no reverse DNS, or one that does not match its hostname, is rejected outright by many large providers.
What is a null MX?
A single record of "0 ." tells senders the domain accepts no mail at all (RFC 7505). It is the correct way to say so, and it makes bounces immediate instead of leaving mail queued for days.