cp04.static.cnode.io has no MX records.
Question and response
Question
dig cp04.static.cnode.io. MX
Answer
The response has no answer records.
Authority
cp04.static.cnode.io. 3600 SOA ns-a1.cnode.io. hostmaster.cnode.io. 2019020701 1800 900 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0