mx.powweb.com has no CNAME records.
Question and response
Question
dig mx.powweb.com. NS
Answer
The response has no answer records.
Authority
powweb.com. 3483 SOA ns3.powweb.com. hostmaster.powweb.com. 1157657014 900 60 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0