smtp3.owe.de has no CNAME records.
Question and response
Question
dig smtp3.owe.de. NS
Answer
The response has no answer records.
Authority
owe.de. 10393 SOA ns.owe.de. hostmaster.owe.de. 2026021700 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0