mail1.cdkglobal.com has no CNAME records.
Question and response
Question
dig mail1.cdkglobal.com. NS
Answer
The response has no answer records.
Authority
cdkglobal.com. 300 SOA ns.ord.us.cdk.com. named.cdk.com. 2026022500 3600 900 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0