mx01-dtx01-opus.opusnet.com has no CNAME records.
Question and response
Question
dig mx01-dtx01-opus.opusnet.com. NS
Answer
The response has no answer records.
Authority
opusnet.com. 600 SOA ns1.opusinteractive.io. sysadmin.opusinteractive.com. 2026012201 5400 600 1209600 5400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0