mx1.completeuc.com has no CNAME records.
Question and response
Question
dig mx1.completeuc.com. NS
Answer
The response has no answer records.
Authority
completeuc.com. 3136 SOA ns01.momentumtelecom.com. systems.momentumtelecom.com. 2025032100 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0