Apex domains cannot have CNAME records.
Question and response
Question
dig resender.email. NS
Answer
resender.email. 5 NS tim.ns.cloudflare.com.
resender.email. 5 NS gene.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0