mx-2.ismt.pt has no CNAME records.
Question and response
Question
dig mx-2.ismt.pt. NS
Answer
The response has no answer records.
Authority
ismt.pt. 3600 SOA ns-1.ismt.pt. gestor.ismt.pt. 2025110700 14400 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0