MX & SMTP test
List a domain's mail servers and confirm the primary answers on SMTP.
Enter a domain to list its MX (mail exchange) records in priority order and confirm the primary mail server is reachable on SMTP (port 25), including its greeting banner. Use it to debug email delivery and verify a new mail setup.
Frequently asked questions
What does the MX priority number mean?
Lower numbers are tried first. Mail is delivered to the lowest-priority (highest-preference) server that answers.
The server didn't answer on 25 — is that bad?
Some networks firewall port 25 or only accept mail from certain sources, so a single test isn't definitive — but a healthy public mail server should respond with a 220 banner.
Should I have more than one MX record?
A backup MX at a higher priority number lets mail queue elsewhere if your primary is briefly down. Many providers handle redundancy behind a single MX hostname, so one record can be fine if that host is highly available.
Why does my MX point to a different domain?
That's normal when you use a hosted email provider — your MX delegates inbound mail to their servers (for example aspmx.l.google.com). The MX hostname just needs valid A/AAAA records and to be reachable on SMTP.
What is the SMTP 220 banner?
It's the greeting a mail server sends right after you connect on port 25, identifying itself and signaling it's ready to receive. Seeing a 220 confirms the server is up and speaking SMTP.
How is this different from a full SMTP diagnostics scan?
This focuses on MX records and a basic connectivity/banner check; the SMTP diagnostics tool goes further, testing STARTTLS support and open-relay exposure on the server.
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