mail.creoline.com has no CNAME records.
Question and response
Question
dig mail.creoline.com. NS
Answer
The response has no answer records.
Authority
creoline.com. 2268 SOA ns1.creoline.net. noc.creoline.com. 2026020615 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0