prov1.busy1.cgocable.net has no MX records.
Question and response
Question
dig prov1.busy1.cgocable.net. MX
Answer
The response has no answer records.
Authority
busy1.cgocable.net. 86400 SOA ns4.cgocable.net. dnsadmin.cgocable.net. 2007014693 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0