smtp.owei.net has no CNAME records.
Question and response
Question
dig smtp.owei.net. NS
Answer
The response has no answer records.
Authority
owei.net. 10142 SOA ns.owe.de. hostmaster.owe.de. 2025041001 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0