ns4.ipowerdns.com has no MX records.
Question and response
Question
dig ns4.ipowerdns.com. MX
Answer
The response has no answer records.
Authority
ipowerdns.com. 3600 SOA ns1.ipowerweb.net. hostmaster.ipowerweb.net. 2002101100 80000 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0