cersrrelay01.callone.com has no MX records.
Question and response
Question
dig cersrrelay01.callone.com. MX
Answer
The response has no answer records.
Authority
callone.com. 300 SOA dns1.easydns.com. zone.easydns.com. 1758297204 3600 600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0