How to make letters sent via mailgun reach mail.ru?

Question

Email

How and what needs to be done so that the letters reach the addressees? Yandex and gmail accept mail normally, mail servers refuse whether it's their own domain on mail.ru or just an address on mail.ru.
The DNS of the domain from which I am sending hangs on Yandex. I send it to mailgun from a subdomain, but it doesn't really exist, but I don't think that's the problem, though... In general, tell me which way to dig and what to configure.
mailgun log

{
  "severity": "permanent",
  "tags": [],
  "delivery-status": {
    "tls": true,
    "mx-host": "mxs.mail.ru",
    "code": 550,
    "description": null,
    "session-seconds": 1.3487091064453125,
    "message": "550 Unroutable sender address",
    "certificate-verified": true
  },
  "envelope": {
    "transport": "smtp",
    "sender": "[email protected]",
    "sending-ip": "184.173.153.221",
    "targets": "[email protected]"
  },
  "recipient-domain": "mail.ru",
  "id": "F8gqqFJ7RBS9YrRWHiKjnA",
  "campaigns": [],
  "reason": "generic",
  "user-variables": {},
  "flags": {
    "is-routed": null,
    "is-authenticated": true,
    "is-system-test": false,
    "is-test-mode": false
  },
  "log-level": "error",
  "timestamp": 1440403555.479207,
  "message": {
    "headers": {
      "to": "[email protected]",
      "message-id": "[email protected]",
      "from": "[email protected]",
      "subject": "Тема письма"
    },
    "attachments": [],
    "recipients": [
      "[email protected]"
    ],
    "size": 4750
  },
  "recipient": "[email protected]",
  "event": "failed"
}

Answer 1

stackoverflow.com/questions/27930771/mailgun-messa...