mail.pjsr.edu.do has no CNAME records.
Question and response
Question
dig mail.pjsr.edu.do. NS
Answer
The response has no answer records.
Authority
pjsr.edu.do. 10800 SOA ns1.pjsr.edu.do. postmaster.pjsr.edu.do. 3050346916 21600 3600 86400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0