mxB.expurgate.de has no CNAME records.
Question and response
Question
dig mxB.expurgate.de. NS
Answer
The response has no answer records.
Authority
expurgate.de. 239 SOA ns1.expurgate.net. admin.expurgate.net. 2026022303 3600 900 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0