mail.carrierops.com has no CNAME records.
Question and response
Question
dig mail.carrierops.com. NS
Answer
The response has no answer records.
Authority
carrierops.com. 2303 SOA ns1.subrigo.net. support.cloudns.net. 2025082102 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0