mx2.dynu.com has no CNAME records.
Question and response
Question
dig mx2.dynu.com. NS
Answer
The response has no answer records.
Authority
dynu.com. 3427 SOA ns1.dynu.com. administrator.dynu.com. 76193390 1800 300 86400 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0