vps.jump4.com has no MX records.
Question and response
Question
dig vps.jump4.com. MX
Answer
The response has no answer records.
Authority
jump4.com. 300 SOA ns1.hover.com. dnsmaster.hover.com. 1720469689 1800 900 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0