Apex domains cannot have CNAME records.
Question and response
Question
dig socketlabs.email-od.com. NS
Answer
socketlabs.email-od.com. 5 NS ns-1974.awsdns-54.co.uk.
socketlabs.email-od.com. 5 NS ns-769.awsdns-32.net.
socketlabs.email-od.com. 5 NS ns-121.awsdns-15.com.
socketlabs.email-od.com. 5 NS ns-1167.awsdns-17.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0