mail.stableserver.net has no NS records.
NS records for this zone are defined at stableserver.net.
NS records for this zone are defined at stableserver.net.
Question and response
Question
dig mail.stableserver.net. NS
Answer
The response has no answer records.
Authority
stableserver.net. 3600 SOA ns1.stableserver.net. postmaster.stableserver.net. 2026022318 3600 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0