dns.cogentco.com has no MX records.
Question and response
Question
dig dns.cogentco.com. MX
Answer
The response has no answer records.
Authority
dns.cogentco.com. 43200 SOA auth1.dns.cogentco.com. dns.cogentco.com. 2026020702 10800 3600 604800 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0