mx4.mxfilter.net has no NS records.
NS records for this zone are defined at mxfilter.net.
NS records for this zone are defined at mxfilter.net.
Question and response
Question
dig mx4.mxfilter.net. NS
Answer
The response has no answer records.
Authority
mxfilter.net. 86400 SOA ns1.private-nameserver.net. admin.namecrane.net. 2025100902 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0