mx1.uberspace.is has no NS records.
NS records for this zone are defined at uberspace.is.
NS records for this zone are defined at uberspace.is.
Question and response
Question
dig mx1.uberspace.is. NS
Answer
The response has no answer records.
Authority
uberspace.is. 2560 SOA ns3.jonaspasche.com. hostmaster.uberspace.is. 1771243981 16384 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0