smtp239.em5service.cz has no NS records.
NS records for this zone are defined at em5service.cz.
NS records for this zone are defined at em5service.cz.
Question and response
Question
dig smtp239.em5service.cz. NS
Answer
The response has no answer records.
Authority
em5service.cz. 1800 SOA ns1.zcom.cz. hostmaster.zcom.cz. 1774242994 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0