mail.semcabo.com has no CNAME records.
Question and response
Question
dig mail.semcabo.com. NS
Answer
The response has no answer records.
Authority
semcabo.com. 10800 SOA dns1.semcabo.pt. mail.semcabo.com. 1163576284 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0