spf.rrz-sued.at has no MX records.
Question and response
Question
dig spf.rrz-sued.at. MX
Answer
The response has no answer records.
Authority
rrz-sued.at. 900 SOA dns1.grz.at. hostmaster.rrz.co.at. 2013093056 1800 600 1209600 900
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0