Apex domains cannot have CNAME records.
Question and response
Question
dig imail.com.BN. NS
Answer
imail.com.BN. 5 NS ns4-08.azure-dns.info.
imail.com.BN. 5 NS ns1-08.azure-dns.com.
imail.com.BN. 5 NS ns2-08.azure-dns.net.
imail.com.BN. 5 NS ns3-08.azure-dns.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0