cdp.mil.do has no MX records.
Question and response
Question
dig cdp.mil.do. MX
Answer
The response has no answer records.
Authority
cdp.mil.do. 1800 SOA karina.ns.cloudflare.com. dns.cloudflare.com. 2397237548 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0