o2.pstemail.knowbe4.com has no NS records.
NS records for this zone are defined at pstemail.knowbe4.com.
NS records for this zone are defined at pstemail.knowbe4.com.
Question and response
Question
dig o2.pstemail.knowbe4.com. NS
Answer
The response has no answer records.
Authority
knowbe4.com. 900 SOA ns-1036.awsdns-01.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0