mailer2.threatsim.com has no NS records.
NS records for this zone are defined at threatsim.com.
NS records for this zone are defined at threatsim.com.
Question and response
Question
dig mailer2.threatsim.com. NS
Answer
The response has no answer records.
Authority
threatsim.com. 900 SOA ns-1653.awsdns-14.co.uk. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0