mx2.brunner.at has no CNAME records.
Question and response
Question
dig mx2.brunner.at. NS
Answer
The response has no answer records.
Authority
brunner.at. 1083 SOA dns1w.brunner.at. admin.brunner.at. 753364853 10800 3600 605000 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0