mx.cogeco.ca has no CNAME records.
Question and response
Question
dig mx.cogeco.ca. NS
Answer
The response has no answer records.
Authority
cogeco.ca. 6598 SOA ns1.cgocable.net. dnsadmin.cgocable.net. 2007688092 1800 7200 86400 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0