mail.coloat.com has no CNAME records.
Question and response
Question
dig mail.coloat.com. NS
Answer
The response has no answer records.
Authority
coloat.com. 3058 SOA ns0.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2008022381 43200 3600 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0