mx1.mailbox.pt has no NS records.
NS records for this zone are defined at mailbox.pt.
NS records for this zone are defined at mailbox.pt.
Question and response
Question
dig mx1.mailbox.pt. NS
Answer
The response has no answer records.
Authority
mailbox.pt. 3600 SOA dns1.host-redirect.com. hostmaster.mailbox.pt. 2026021801 3600 600 604800 3600
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0