mx-por.iptelecom.pt has no NS records.
NS records for this zone are defined at iptelecom.pt.
NS records for this zone are defined at iptelecom.pt.
Question and response
Question
dig mx-por.iptelecom.pt. NS
Answer
The response has no answer records.
Authority
iptelecom.pt. 900 SOA dns.refertelecom.pt. root.refertelecom.pt. 2026010601 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0