mx.marin.ad has no CNAME records.
Question and response
Question
dig mx.marin.ad. NS
Answer
The response has no answer records.
Authority
marin.ad. 3182 SOA pns61.cloudns.net. support.cloudns.net. 2026010101 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0