mail.furanet.com has no CNAME records.
Question and response
Question
dig mail.furanet.com. NS
Answer
The response has no answer records.
Authority
furanet.com. 227 SOA dns1.hispalisdns.com. admin.furanet.com. 2026030607 3200 1600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0