mx20.antispam.mailspamprotection.com has no NS records.
NS records for this zone are defined at antispam.mailspamprotection.com.
NS records for this zone are defined at antispam.mailspamprotection.com.
Question and response
Question
dig mx20.antispam.mailspamprotection.com. NS
Answer
The response has no answer records.
Authority
antispam.mailspamprotection.com. 300 SOA ns-cloud-a1.googledomains.com. cloud-dns-hostmaster.google.com. 1 21600 3600 259200 300
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0