at.cox.net has no MX records.
Question and response
Question
dig at.cox.net. MX
Answer
The response has no answer records.
Authority
at.cox.net. 86400 SOA dukensumpov1z.services.cox.net. hostmaster.cox.net. 781212537 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0