outbound-smtp56.blacknight.com has no NS records.
NS records for this zone are defined at blacknight.com.
NS records for this zone are defined at blacknight.com.
Question and response
Question
dig outbound-smtp56.blacknight.com. NS
Answer
The response has no answer records.
Authority
blacknight.com. 3600 SOA ns1.blacknight.com. hostmaster.blacknight.com. 1276188654 14400 7200 2419200 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0