FINDINGemail.
Jump to what to doemail.null_mx
The domain explicitly declares, via RFC 7505, that it accepts no mail.
What it looks at#
The same DNS-over-HTTPS MX query as email.no_mx. If the
domain publishes exactly one MX record with preference 0 and exchange ., that’s RFC
7505’s “null MX” — a domain owner’s explicit machine-readable statement that the domain
does not, and will not, accept email.
Why it matters#
This isn’t a misconfiguration or an oversight the domain might fix later — it’s a deliberate declaration. Nothing sent to an address at this domain will ever be delivered, by design.
What to do#
High severity blocks by default. Unlike email.no_mx, there’s no ambiguity about whether
this might be temporary — treat it the same as a domain that has stated in writing it
doesn’t do email.