ns4.dnepro.net has no MX records.
Question and response
Question
dig ns4.dnepro.net. MX
Answer
The response has no answer records.
Authority
dnepro.net. 1800 SOA ns.dnepro.net. root.dnepro.net. 2016062734 36000 300 60480 8640
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0