mx3.wkglobal.com has no NS records.
NS records for this zone are defined at wkglobal.com.
NS records for this zone are defined at wkglobal.com.
Question and response
Question
dig mx3.wkglobal.com. NS
Answer
The response has no answer records.
Authority
wkglobal.com. 900 SOA ns-1590.awsdns-06.co.uk. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0