Apex domains cannot have CNAME records.
Question and response
Question
dig stampymail.com. NS
Answer
stampymail.com. 5 NS ns1.stampymail.com.
stampymail.com. 5 NS ns2.stampymail.com.
Authority
The response has no authority records.
Additional
ns1.stampymail.com. 5 A 93.174.0.7
ns2.stampymail.com. 5 A 93.174.0.7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0