spf.vtx.ch has no NS records.
NS records for this zone are defined at vtx.ch.
NS records for this zone are defined at vtx.ch.
Question and response
Question
dig spf.vtx.ch. NS
Answer
The response has no answer records.
Authority
vtx.ch. 86046 SOA ns01.vtx.ch. dnsmaster.vtx.ch. 2026020205 21600 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0