mxp.meo.pt has no CNAME records.
Question and response
Question
dig mxp.meo.pt. NS
Answer
The response has no answer records.
Authority
meo.pt. 300 SOA dnscoi1aut01.local. dns.mail.telepac.pt. 2023083939 300 300 300 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0