mail01.sasender.net has no NS records.
NS records for this zone are defined at sasender.net.
NS records for this zone are defined at sasender.net.
Question and response
Question
dig mail01.sasender.net. NS
Answer
The response has no answer records.
Authority
sasender.net. 3600 SOA a.portsdns.se. registry.ports.net. 2025102400 1800 900 1814400 3600
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0