mail6420.mkt7019.com has no NS records.
NS records for this zone are defined at mkt7019.com.
NS records for this zone are defined at mkt7019.com.
Question and response
Question
dig mail6420.mkt7019.com. NS
Answer
The response has no answer records.
Authority
mkt7019.com. 900 SOA ns1.acoustic-adm.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0