mail.astendo.de has no CNAME records.
Question and response
Question
dig mail.astendo.de. NS
Answer
The response has no answer records.
Authority
astendo.de. 10800 SOA ns3.ip-projects.de. do-not-reply.astendo.de. 2026011507 43200 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0