mx1.cloudk.pt has no CNAME records.
Question and response
Question
dig mx1.cloudk.pt. NS
Answer
The response has no answer records.
Authority
cloudk.pt. 59 SOA ns1.bizview.pt. dc.cloudkey.pt. 2026021801 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0