mail.lewron.de has no CNAME records.
Question and response
Question
dig mail.lewron.de. NS
Answer
The response has no answer records.
Authority
lewron.de. 41 SOA docks03.rzone.de. hostmaster.strato-rz.de. 2023060732 86400 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0