What is checked?
The check examines DNS foundations and MX target resolution. An MX points to a hostname with A or AAAA addresses. Lower priority numbers are preferred. Null MX (0 .) explicitly states that a domain accepts no email and must not be mixed with regular MX targets.
Worked example
Synthetic example using a reserved domain and documentation addresses. Adapt the domain, addresses and services to your infrastructure before using it.
example.test. MX 10 mx.example.test.
mx.example.test. A 192.0.2.10example.test directs incoming mail to mx.example.test. The IP shown is a documentation address, not a reachable mail server.
Common mistake
An existing MX is mistaken for proof of authorized sending or a valid SMTP certificate. Those require SPF/DKIM evidence or a separate TLS connection measurement.
Recommended next step
Confirm receiving targets with the operator and check their A/AAAA resolution. Correct missing or obsolete DNS targets. After domain verification, enabled monitoring can also provide stored SMTP/TLS measurements.
What the result does not prove
The anonymous DNS check does not establish an SMTP connection. It cannot confirm mail service availability, acceptance of a message or certificate validity.