ks.cox.net has no MX records.
Question and response
Question
dig ks.cox.net. MX
Answer
The response has no answer records.
Authority
ks.cox.net. 86400 SOA dukensumpov1z.services.cox.net. hostmaster.cox.net. 781212277 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0