hsd1.co.comcast.net has no MX records.
Question and response
Question
dig hsd1.co.comcast.net. MX
Answer
The response has no answer records.
Authority
hsd1.co.comcast.net. 900 SOA dns101.comcast.net. dnsadmin.comcast.net. 12636794 7200 3600 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0