smtp.yopmail.com has no NS records.
NS records for this zone are defined at yopmail.com.
NS records for this zone are defined at yopmail.com.
Question and response
Question
dig smtp.yopmail.com. NS
Answer
The response has no answer records.
Authority
yopmail.com. 86400 SOA dns14.ovh.net. tech.ovh.net. 2026032501 86400 3600 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0