mx20.utp.edu.pl has no NS records.
NS records for this zone are defined at utp.edu.pl.
NS records for this zone are defined at utp.edu.pl.
Question and response
Question
dig mx20.utp.edu.pl. NS
Answer
The response has no answer records.
Authority
utp.edu.pl. 900 SOA sun1.utp.edu.pl. please_set_email.absolutely.nowhere. 2011046281 10800 3600 2419200 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0