mx1.orlen.pl has no NS records.
NS records for this zone are defined at orlen.pl.
NS records for this zone are defined at orlen.pl.
Question and response
Question
dig mx1.orlen.pl. NS
Answer
The response has no answer records.
Authority
orlen.pl. 900 SOA dns1.orlen.pl. help.orlen.pl. 2019071919 86400 14400 2592000 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0