spf.seznam.cz has no NS records.
NS records for this zone are defined at seznam.cz.
NS records for this zone are defined at seznam.cz.
Question and response
Question
dig spf.seznam.cz. NS
Answer
The response has no answer records.
Authority
seznam.cz. 300 SOA ans.seznam.cz. hostmaster.seznam.cz. 1774201994 900 300 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0