nsk.as15800.net has no MX records.
Question and response
Question
dig nsk.as15800.net. MX
Answer
The response has no answer records.
Authority
as15800.net. 3600 SOA ns.net.ua. hostmaster.eunic.net.ua. 2026012601 3600 1800 1209600 3600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0