smtp.namedserver.net has no CNAME records.
Question and response
Question
dig smtp.namedserver.net. NS
Answer
The response has no answer records.
Authority
namedserver.net. 1425 SOA ns.namedserver.net. root.ns.namedserver.net. 2705556054 10800 1800 259200 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0