mail2.shopup.com has no NS records.
NS records for this zone are defined at shopup.com.
NS records for this zone are defined at shopup.com.
Question and response
Question
dig mail2.shopup.com. NS
Answer
The response has no answer records.
Authority
shopup.com. 3600 SOA ns1. hostmaster. 20101289 900 600 86400 3600
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0