hfc.comcastbusiness.net has no MX records.
Question and response
Question
dig hfc.comcastbusiness.net. MX
Answer
The response has no answer records.
Authority
hfc.comcastbusiness.net. 900 SOA ns.hfc.comcastbusiness.net. dnsmaster.comcastonline.com. 2022956822 7200 300 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0