mail05.ch.umantis.com has no CNAME records.
Question and response
Question
dig mail05.ch.umantis.com. NS
Answer
The response has no answer records.
Authority
umantis.com. 1591 SOA ns1.umantis.com. hostmaster.umantis.com. 2026022501 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0