mx1.cpanel.net has no CNAME records.
Question and response
Question
dig mx1.cpanel.net. NS
Answer
The response has no answer records.
Authority
cpanel.net. 261 SOA c.cpanel.net. dns.cpanel.net. 2026030901 1200 7200 1600000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0