www.om.cox.net has no MX records.
Question and response
Question
dig www.om.cox.net. MX
Answer
The response has no answer records.
Authority
om.cox.net. 86400 SOA dukensumpov1z.services.cox.net. hostmaster.cox.net. 781212273 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0