sdn57.xmailse.com has no NS records.
NS records for this zone are defined at xmailse.com.
NS records for this zone are defined at xmailse.com.
Question and response
Question
dig sdn57.xmailse.com. NS
Answer
The response has no answer records.
Authority
xmailse.com. 900 SOA ns-1834.awsdns-37.co.uk. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0