s1.mx.mta1.net has no CNAME records.
Question and response
Question
dig s1.mx.mta1.net. NS
Answer
The response has no answer records.
Authority
mta1.net. 3600 SOA dns41.cloudns.net. support.cloudns.net. 2024032356 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0