ns.iol.sk has no MX records.
Question and response
Question
dig ns.iol.sk. MX
Answer
The response has no answer records.
Authority
iol.sk. 86400 SOA ns.iol.sk. root.iol.sk. 2025100901 28800 14400 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0