mx2.infoserve.de has no CNAME records.
Question and response
Question
dig mx2.infoserve.de. NS
Answer
The response has no answer records.
Authority
infoserve.de. 250 SOA dns1.infoserve.de. hostmaster.infoserve.de. 2026021207 28800 7200 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0