smtpv4.setr7p.cz has no NS records.
NS records for this zone are defined at setr7p.cz.
NS records for this zone are defined at setr7p.cz.
Question and response
Question
dig smtpv4.setr7p.cz. NS
Answer
The response has no answer records.
Authority
setr7p.cz. 900 SOA ns-757.awsdns-30.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0