No MX record — this domain cannot receive email
What this check looks for
Your domain publishes no mail server records, so nobody can send email to any address at it. Messages bounce back to the sender.
Why it matters
If you expect to receive mail at this domain, it is currently being lost. If you do not, publishing a null MX makes that explicit and stops spammers using your domain as a fake return address.
When the check passes, your report says: “The domain publishes mail servers and can receive email”.
What it costs your score
When this check fails it removes 30 points from your Email transport score, before the status, confidence and repeat multipliers are applied. Email transport carries a weight of 8 in the overall score.
It shares the email-transport.mx family ceiling of 30 points: however many findings that family produces, together they cannot remove more than that from Email transport. One underlying problem showing up in several places is still one problem.
- Severity
- critical
- Default confidence
- confirmed
- Status when triggered
- fail
- Deduction
- 30 points
- Family cap
- email-transport.mx · 30
- Category
- Email transport
- Module
- Email mx
- Fix owned by
- dns host
- In the ruleset since
- 2026.09
How to fix it
Publish the MX records your mail provider documents, or a null MX if the domain sends no mail.
Without MX records, inbound mail to this domain bounces.
If you use a hosted mailbox provider, copy the MX records from their setup page — the generator has presets for the major ones.
If the domain is not meant to receive mail, publish a null MX: a single MX record with priority 0 and a target of
..
How to confirm it worked
dig +short MX ‹domain› — expect at least one host, or a single '0 .' for a null MX
Send a test message to an address at ‹domain› and confirm it is delivered.
{{domain}}. 3600 IN MX 10 {{mxHost}}.A named slot like ‹domain› — and the braces left in the configuration below — is filled in with your own values when this rule appears on a report.
Remediation by platform
‹domain›. 3600 IN MX 10 ‹mx host›.‹domain›. 3600 IN MX 0 ‹tenant›.mail.protection.outlook.com.‹domain›. 3600 IN MX 1 smtp.google.com.Technical detail
No MX records were returned for ‹domain›. RFC 5321 §5.1 allows a sender to fall back to the A/AAAA address of the domain when no MX exists — ‹fallback note› — but this implicit fallback is widely disabled and should never be relied on. A domain that genuinely does not receive mail should publish a null MX per RFC 7505.
Standards and references
Test this on your domain
Run the check that produces this finding, on its own, against any domain.
Other email mx checks
- Two MX hosts share the same preference value
- MX record points at a CNAME
- MX record points at an IP address instead of a hostname
- Mail server address has no reverse DNS name
- MX host does not resolve to an address
- Every mail server resolves to the same address
- Domain publishes a null MX (receives no mail)
- Only one mail server host is published