mail.usn.edu.do has no CNAME records.
Question and response
Question
dig mail.usn.edu.do. NS
Answer
The response has no answer records.
Authority
usn.edu.do. 17 SOA ns1411.websitewelcome.com. gerencia.teldiux.com. 2026020101 86400 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0