mail.superdnsserver.net has no CNAME records.
Question and response
Question
dig mail.superdnsserver.net. NS
Answer
The response has no answer records.
Authority
superdnsserver.net. 615 SOA ns1.superdnsserver.net. hostmaster.superhosting.bg. 2013076245 3600 600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0