mail2.netcabo.pt has no CNAME records.
Question and response
Question
dig mail2.netcabo.pt. NS
Answer
The response has no answer records.
Authority
netcabo.pt. 1680 SOA kianchau.ns.cloudflare.com. dns.cloudflare.com. 2397141305 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0