About
Enter a domain and read back the hosts that accept mail for it, each with its priority. This is the first question to settle when mail is going missing, because everything downstream assumes you know where it was supposed to arrive.
How to use
Enter the domain on its own, with no protocol and no address prefix. Take a hostname from the results into the SMTP test when you want to know whether that server is answering.
Priority, and the order servers are tried
Each MX record carries a number, and senders work from the lowest upward. Ten and twenty is the usual pattern: the first takes the traffic, the second exists for when the first is unreachable. Equal numbers mean the load is shared between them. A backup that has quietly stopped working is invisible until the primary fails, which is when it matters most.
What a wrong answer looks like
Two providers listed at once is the classic finding, and it happens after a migration where the old records were never removed. Mail then arrives at whichever host answered, which explains messages that reach one mailbox and not another. A hostname that no longer resolves is the other common case, and it produces delivery failures that mention a name nobody at the company recognises.
From a record to a working connection
An MX record is a claim about where mail should go, not proof that anything is there. Take the hostname it returns and open a short SMTP session against it to see whether a server answers and what it advertises. That two step sequence separates a DNS problem from a server problem, and it is quicker than reading bounce messages.
FAQ
Is a lower priority number better?
Yes, and the wording trips everyone up. The lowest number is tried first. Higher numbers are backups that normally sit idle.
This domain has no MX record at all.
Some small domains still receive on their A record, which the standard permits. Most senders treat a missing MX as undeliverable anyway, so for a domain that expects mail it should be treated as a configuration error.
How is this different from the general DNS lookup?
The DNS lookup returns many record types at once. This one returns mail routing alone, which is the view you want when the question is about delivery.
The result does not match what my provider told me to set.
Compare the exact hostnames including any trailing dot, and check whether an old provider's records were left in place alongside the new ones.
Related tools
- Email tools
- Gmail Address Checker
Check up to ten Gmail addresses per run.
- Outlook Mail Reader
Read recent mail using your own refresh token.
- SMTP Test
Open a short SMTP session and read the banner.
- Email Header Analyzer
Parse Received hops and auth lines locally.
- DNS Lookup
Public A, AAAA, CNAME, MX, TXT and NS records.