mail4.netdesignmail.com has no NS records.
NS records for this zone are defined at netdesignmail.com.
NS records for this zone are defined at netdesignmail.com.
Question and response
Question
dig mail4.netdesignmail.com. NS
Answer
The response has no answer records.
Authority
netdesignmail.com. 3600 SOA ns1. hostmaster. 22 900 600 86400 3600
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0