ns2.rrze.uni-erlangen.de has no MX records.
Question and response
Question
dig ns2.rrze.uni-erlangen.de. MX
Answer
The response has no answer records.
Authority
uni-erlangen.de. 3600 SOA ns1.rrze.uni-erlangen.de. hostmaster.rrze.uni-erlangen.de. 1773074189 10800 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0