mail1.o2imt.de has no CNAME records.
Question and response
Question
dig mail1.o2imt.de. NS
Answer
The response has no answer records.
Authority
o2imt.de. 7200 SOA ns2.syzygy.de. hostmaster.syzygy.de. 2016101710 10800 1800 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0