smtp.21vianet.com has no NS records.
NS records for this zone are defined at 21vianet.com.
NS records for this zone are defined at 21vianet.com.
Question and response
Question
dig smtp.21vianet.com. NS
Answer
The response has no answer records.
Authority
21vianet.com. 600 SOA vip3.alidns.com. hostmaster.hichina.com. 2025121011 3600 1200 86400 600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0