fra1.m3connect.de has no MX records.
Question and response
Question
dig fra1.m3connect.de. MX
Answer
The response has no answer records.
Authority
fra1.m3connect.de. 86400 SOA ns1.fra1.m3connect.de. hostmaster.m3connect.de. 2025090100 14400 3600 604800 86400
Additional
. 0 OPT [{Extended_DNS_Error: PROHIBITED}] ; payload 1232, xrcode 0, version 0, flags 0