smtpv3.seh6tr.cz has no NS records.
NS records for this zone are defined at seh6tr.cz.
NS records for this zone are defined at seh6tr.cz.
Question and response
Question
dig smtpv3.seh6tr.cz. NS
Answer
The response has no answer records.
Authority
seh6tr.cz. 900 SOA ns-115.awsdns-14.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0