mail2.semcabo.pt has no CNAME records.
Question and response
Question
dig mail2.semcabo.pt. NS
Answer
The response has no answer records.
Authority
semcabo.pt. 3254 SOA dns1.semcabo.pt. mail.semcabo.pt. 1161100513 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0