host.vnet.sk has no MX records.
Question and response
Question
dig host.vnet.sk. MX
Answer
The response has no answer records.
Authority
host.vnet.sk. 3600 SOA ns.vnet.sk. hostmaster.vnet.sk. 2018072000 3600 900 259200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0