mx01.mirex.gob.do has no CNAME records.
Question and response
Question
dig mx01.mirex.gob.do. NS
Answer
The response has no answer records.
Authority
mirex.gob.do. 1775 SOA emerie.ns.cloudflare.com. dns.cloudflare.com. 2396943355 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0