mx.colocall.net has no CNAME records.
Question and response
Question
dig mx.colocall.net. NS
Answer
The response has no answer records.
Authority
colocall.net. 3387 SOA ns1.colocall.net. hostmaster.colocall.net. 2026021600 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0