mx-1.cronoshield.net has no CNAME records.
Question and response
Question
dig mx-1.cronoshield.net. NS
Answer
The response has no answer records.
Authority
cronoshield.net. 3237 SOA ns1.cronosinternet.net. support.cronosinternet.net. 2015111201 3600 300 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0