mail1.resvoip.cableone.net has no MX records.
Question and response
Question
dig mail1.resvoip.cableone.net. MX
Answer
The response has no answer records.
Authority
cableone.net. 300 SOA ns1.cableone.net. tech.cableone.net. 1903 300 300 300 300
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0