tls.not_applicable
TLS Not Applicable (Null MX)
What we check
We determine whether TLS checks are applicable based on the domain's MX configuration. When a domain publishes a Null MX record (RFC 7505), it declares that it does not accept email — there are no mail servers to test.
What this finding means
The domain has a valid Null MX record, so TLS testing does not apply. There are no SMTP servers to connect to, no certificates to verify, and no STARTTLS to negotiate. This is not a deficiency — it is the correct result for a domain that deliberately does not accept email.
Evidence example
$ dig +short MX example.com
0 .
Null MX — domain does not accept email, TLS checks not applicable