mail.sdq.edu.do has no MX records.
Question and response
Question
dig mail.sdq.edu.do. MX
Answer
The response has no answer records.
Authority
sdq.edu.do. 300 SOA ns1.bluehost.com. root.box2440.bluehost.com. 2021032000 86400 7200 3600000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0