_netblocks.skynet.cz has no MX records.
Question and response
Question
dig _netblocks.skynet.cz. MX
Answer
The response has no answer records.
Authority
skynet.cz. 3600 SOA ns1.poda.cz. hostmaster.poda.cz. 2026010602 3600 1800 2529000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0