MX hosts resolve to public addresses
mail.mx-resolves
An MX that does not resolve, or resolves to a private address, cannot receive mail from the internet.
A longer write-up of this check has not been published yet. The report itself shows the raw evidence behind every result, which is usually the fastest way to see what was measured.
Run this check on a domain
MX hosts resolve to public addresses is one of 49 checks in every report, alongside delegation, mail authentication, TLS and registration.