mail.zv.tum.de has no MX records.
Question and response
Question
dig mail.zv.tum.de. MX
Answer
The response has no answer records.
Authority
zv.tum.de. 86400 SOA dns1.lrz.de. hostmaster.lrz.de. 2026022606 10800 3600 1814400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0