mbx231.completeuc.com has no CNAME records.
Question and response
Question
dig mbx231.completeuc.com. NS
Answer
The response has no answer records.
Authority
completeuc.com. 3600 SOA ns01.momentumtelecom.com. systems.momentumtelecom.com. 2026022300 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0