cx.spamfree.cz has no NS records.
NS records for this zone are defined at spamfree.cz.
NS records for this zone are defined at spamfree.cz.
Question and response
Question
dig cx.spamfree.cz. NS
Answer
The response has no answer records.
Authority
spamfree.cz. 1800 SOA cora.ns.cloudflare.com. dns.cloudflare.com. 2399292124 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0