Apex domains cannot have CNAME records.
Question and response
Question
dig mail.edu.do. NS
Answer
mail.edu.do. 5 NS ns1.ikexie.net.
mail.edu.do. 5 NS ns4.ikexie.net.
mail.edu.do. 5 NS ns3.ikexie.net.
mail.edu.do. 5 NS ns2.ikexie.net.
Authority
The response has no authority records.
Additional
ns1.ikexie.net. 5 A 185.136.96.99
ns2.ikexie.net. 5 A 185.136.97.99
ns3.ikexie.net. 5 A 185.136.98.99
ns4.ikexie.net. 5 A 185.136.99.99
ns1.ikexie.net. 5 AAAA 2a06:fb00:1:0:0:0:1:99
ns2.ikexie.net. 5 AAAA 2a06:fb00:1:0:0:0:2:99
ns3.ikexie.net. 5 AAAA 2a06:fb00:1:0:0:0:3:99
ns4.ikexie.net. 5 AAAA 2a06:fb00:1:0:0:0:4:99
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0