Apex domains cannot have CNAME records.
Question and response
Question
dig e-mail-spooling.net. NS
Answer
e-mail-spooling.net. 1 NS ns2.chi1.etrn.com.
e-mail-spooling.net. 1 NS ns2.chi3.etrn.com.
e-mail-spooling.net. 1 NS ns1.chi1.etrn.com.
e-mail-spooling.net. 1 NS ns1.chi3.etrn.com.
Authority
The response has no authority records.
Additional
ns1.chi1.etrn.com. 1 A 204.62.29.253
ns1.chi3.etrn.com. 1 A 204.62.30.253
ns2.chi1.etrn.com. 1 A 45.56.69.153
ns2.chi3.etrn.com. 1 A 204.62.28.253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0