Based on my logs, I show that both of your messages were successfully relayed from our systems to 143.166.224.193, so from what we can tell the message was processed successfully.
Because the messages are using our standard addressing format, the from addresses would have been as follows:
D-4-597601-926684-2-1-US2-38CF8837@xmr4.com
D-5-597601-975445-2-1-US2-B8D5FF56@xmr4.com
If I had to guess, I'd say that there is some sort of filter in the way that is causing the messages not to be delivered; either it doesn't like the "weird" from address format, or maybe the @xmr4.com domain needs to be whitelisted to allow the mail through.
I would recommend asking your mail administrators to investigate what happened to the incoming emails.
thanks!!