Apex domains cannot have CNAME records.
Question and response
Question
dig mail.timico.net. NS
Answer
mail.timico.net. 5 NS ns-1166.awsdns-17.org.
mail.timico.net. 5 NS ns-230.awsdns-28.com.
mail.timico.net. 5 NS ns-708.awsdns-24.net.
mail.timico.net. 5 NS ns-1549.awsdns-01.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0