rm01.hostpress.de has no NS records.
NS records for this zone are defined at hostpress.de.
NS records for this zone are defined at hostpress.de.
Question and response
Question
dig return-cname.emailsys.net. NS
Answer
The response has no answer records.
Authority
emailsys.net. 180 SOA ns10.digicertdns.com. dns.digicertdns.com. 2009010521 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0