mail4.netdesignmail.com has no CNAME records.
Question and response
Question
dig mail4.netdesignmail.com. NS
Answer
The response has no answer records.
Authority
netdesignmail.com. 255 SOA ns1. hostmaster. 22 900 600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0