Apex domains cannot have CNAME records.
Question and response
Question
dig autodiscover.info. NS
Answer
autodiscover.info. 5 NS ns2.aname.net.
autodiscover.info. 5 NS ns.aname.net.
autodiscover.info. 5 NS ns3.aname.se.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0