mxs.mirohost.net has no CNAME records.
Question and response
Question
dig mxs.mirohost.net. NS
Answer
The response has no answer records.
Authority
mirohost.net. 900 SOA nsa2.srv53.net. support.dnshosting.org. 1772796729 1800 600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0