mgw01.ironmountain.com.pl has no NS records.
NS records for this zone are defined at ironmountain.com.pl.
NS records for this zone are defined at ironmountain.com.pl.
Question and response
Question
dig mgw01.ironmountain.com.pl. NS
Answer
The response has no answer records.
Authority
ironmountain.com.pl. 900 SOA nusdnsgm01.ironmountain.com. webmaster.ironmountain.com. 185 10800 3600 2592000 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0