mail.abstio.com has no NS records.
NS records for this zone are defined at abstio.com.
NS records for this zone are defined at abstio.com.
Question and response
Question
dig mail.abstio.com. NS
Answer
The response has no answer records.
Authority
abstio.com. 3601 SOA dns1.registrar-servers.com. hostmaster.registrar-servers.com. 1772470389 43200 3600 604800 3601
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0