mail.jetc.edu.do has no CNAME records.
Question and response
Question
dig mail.jetc.edu.do. NS
Answer
The response has no answer records.
Authority
jetc.edu.do. 9289 SOA ns4235.hostgator.com. root.gator2118.hostgator.com. 2026030101 86400 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0