mx.missing

No MX Records

What we check

We query DNS for MX records at the domain. MX records tell sending servers where to deliver email. We also check for A/AAAA records as a fallback — RFC 5321 §5.1 allows a domain without MX records to receive mail at its own address record, but only if such a record exists.

What this finding means

The domain has no MX records and no A/AAAA record to fall back on. No sending server can determine where to deliver email for this domain — mail is undeliverable.

This is distinct from a Null MX (mx.null_mx), which is a deliberate declaration that the domain does not accept email. A missing MX with no fallback is ambiguous: it might be intentional, or it might be a DNS misconfiguration.

Why it matters

All inbound mail fails. Every message sent to any address at this domain will bounce with a permanent delivery failure.
Domain credibility. A domain that cannot receive email raises questions about its legitimacy — email is the baseline internet identity signal.
Bounced replies. If the domain sends outgoing mail (transactional email, newsletters), recipients cannot reply, and automated bounce notifications have nowhere to go.

How to fix

Add MX records pointing to your mail server or provider:

example.com.  IN  MX  10  mail.example.com.
example.com.  IN  MX  20  mail2.example.com.

If the domain should not receive email, publish a Null MX record instead (RFC 7505) to declare that explicitly:
```
example.com.  IN  MX  0  .
```

Verify:

dig +short MX example.com
# Expected: 10 mail.example.com.  (or your provider's MX targets)

How it's graded

Missing MX records carry a 40-point deduction and trigger an instant F grade for the MX category. A domain that cannot receive mail is a fundamental configuration failure. See Grading Methodology for the full scoring model.

Evidence example

$ dig +short MX example.com
(empty)
$ dig +short A example.com
(empty)
No MX records and no A/AAAA fallback — mail is undeliverable