Apex domains cannot have CNAME records.
Question and response
Question
dig zohomail.eu. NS
Answer
zohomail.eu. 5 NS ns41.zns-53.net.
zohomail.eu. 5 NS ns31.zns-53.com.
zohomail.eu. 5 NS ns21.zns-53.net.
zohomail.eu. 5 NS pdns90.ultradns.biz.
zohomail.eu. 5 NS ns1.zohocorp.com.
zohomail.eu. 5 NS ns11.zns-53.com.
zohomail.eu. 5 NS pdns90.ultradns.com.
zohomail.eu. 5 NS pdns90.ultradns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0