mx-asp.srv.infos.de has no CNAME records.
Question and response
Question
dig mx-asp.srv.infos.de. NS
Answer
The response has no answer records.
Authority
infos.de. 300 SOA dns1.infoserve.de. hostmaster.infoserve.de. 2026022300 28800 7200 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0