smtp2a.gdsx.com has no NS records.
NS records for this zone are defined at gdsx.com.
NS records for this zone are defined at gdsx.com.
Question and response
Question
dig smtp2a.gdsx.com. NS
Answer
The response has no answer records.
Authority
gdsx.com. 900 SOA ns-808.awsdns-37.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0