mx03.mi.com.co has no CNAME records.
Question and response
Question
dig mx03.mi.com.co. NS
Answer
The response has no answer records.
Authority
mi.com.co. 229 SOA quincy.ns.cloudflare.com. dns.cloudflare.com. 2397002696 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0