_out.smtp.seeweb.it has no CNAME records.
Question and response
Question
dig _out.smtp.seeweb.it. NS
Answer
The response has no answer records.
Authority
seeweb.it. 10800 SOA dns.seeweb.it. hostmaster.seeweb.it. 2026022600 86400 7200 2592000 21600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0