mail1.email42.de has no CNAME records.
Question and response
Question
dig mail1.email42.de. NS
Answer
The response has no answer records.
Authority
email42.de. 138 SOA ns.pop-hannover.de. hostmaster.net.de. 2026011000 21600 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0