mx1.netart.com has no CNAME records.
Question and response
Question
dig mx1.netart.com. NS
Answer
The response has no answer records.
Authority
netart.com. 3190 SOA ns1.netart.com. office.netart.com. 2008133200 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0