cisco.net.do has no MX records.
Question and response
Question
dig cisco.net.do. MX
Answer
The response has no answer records.
Authority
cisco.net.do. 86400 SOA ns1.markmonitor.com. hostmaster.markmonitor.com. 2019011801 86400 3600 2592000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0