mail.netdesignapp.com has no CNAME records.
Question and response
Question
dig mail.netdesignapp.com. NS
Answer
The response has no answer records.
Authority
netdesignapp.com. 2681 SOA ns1. hostmaster. 16 900 600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0