mx.citycom-austria.com has no CNAME records.
Question and response
Question
dig mx.citycom-austria.com. NS
Answer
The response has no answer records.
Authority
citycom-austria.com. 3600 SOA ns1.grazkom.at. hostmaster.grazkom.at. 2011082800 10800 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0