smtp.leidenuniv.nl has no NS records.
NS records for this zone are defined at leidenuniv.nl.
NS records for this zone are defined at leidenuniv.nl.
Question and response
Question
dig smtp.leidenuniv.nl. NS
Answer
The response has no answer records.
Authority
leidenuniv.nl. 7200 SOA arachne.leidenuniv.nl. postmaster.leidenuniv.nl. 2006745973 10800 1080 2592000 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0