prod4.sitexo.com has no NS records.
NS records for this zone are defined at sitexo.com.
NS records for this zone are defined at sitexo.com.
Question and response
Question
dig prod4.sitexo.com. NS
Answer
The response has no answer records.
Authority
sitexo.com. 900 SOA ns-754.awsdns-30.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0