nussmtp02.ironmountain.com has no NS records.
NS records for this zone are defined at ironmountain.com.
NS records for this zone are defined at ironmountain.com.
Question and response
Question
dig nussmtp02.ironmountain.com. NS
Answer
The response has no answer records.
Authority
ironmountain.com. 900 SOA nusdnsgm01.ironmountain.com. please_set_email.absolutely.nowhere. 2005448177 10800 1080 1728000 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0