mail.mc.net.co has no CNAME records.
Question and response
Question
dig mail.mc.net.co. NS
Answer
The response has no answer records.
Authority
mc.net.co. 10800 SOA name1.mediacommerce.com.co. centrodegestion.mc.net.co. 3634229484 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0