smtp.fido.net has no CNAME records.
Question and response
Question
dig smtp.fido.net. NS
Answer
The response has no answer records.
Authority
fido.net. 600 SOA ns0.server.fido.net. hostmaster.fido.net. 2026022500 7200 3600 1209600 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0