mx2.semcabo.pt has no NS records.
NS records for this zone are defined at semcabo.pt.
NS records for this zone are defined at semcabo.pt.
Question and response
Question
dig fallbackmx.spamexperts.eu. NS
Answer
The response has no answer records.
Authority
spamexperts.eu. 900 SOA ns-310.awsdns-38.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0