ns5.mainloop.net has no CNAME records.
Question and response
Question
dig ns5.mainloop.net. NS
Answer
The response has no answer records.
Authority
mainloop.net. 576 SOA ns1.mainloop.net. hostmaster.mainloop.net. 3959 600 100 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0