mail.int-tech.de has no CNAME records.
Question and response
Question
dig mail.int-tech.de. NS
Answer
The response has no answer records.
Authority
int-tech.de. 71 SOA ns.inttech.de. info.int-tech.de. 2015062504 300 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0