smtp.optimaitalia.com has no CNAME records.
Question and response
Question
dig smtp.optimaitalia.com. NS
Answer
The response has no answer records.
Authority
optimaitalia.com. 600 SOA ns1.optimaitalia.com. noc.optimaitalia.com. 1229842182 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0