fra.pay1.de has no MX records.
Question and response
Question
dig fra.pay1.de. MX
Answer
The response has no answer records.
Authority
pay1.de. 3600 SOA edns1.ultradns.com. hostmaster.payone.com. 2272967942 28800 7200 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0