Apex domains cannot have CNAME records.
Question and response
Question
dig mlbox.email. NS
Answer
mlbox.email. 5 NS rodney.ns.cloudflare.com.
mlbox.email. 5 NS carla.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
rodney.ns.cloudflare.com. 3 A 108.162.193.228
rodney.ns.cloudflare.com. 3 A 172.64.33.228
rodney.ns.cloudflare.com. 3 A 173.245.59.228
rodney.ns.cloudflare.com. 3 AAAA 2606:4700:58:0:0:0:adf5:3be4
rodney.ns.cloudflare.com. 3 AAAA 2803:f800:50:0:0:0:6ca2:c1e4
rodney.ns.cloudflare.com. 3 AAAA 2a06:98c1:50:0:0:0:ac40:21e4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0