Apex domains cannot have CNAME records.
Question and response
Question
dig playbackmail.com. NS
Answer
playbackmail.com. 3 NS ns-406.awsdns-50.com.
playbackmail.com. 3 NS ns-1640.awsdns-13.co.uk.
playbackmail.com. 3 NS ns-1383.awsdns-44.org.
playbackmail.com. 3 NS ns-722.awsdns-26.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0