I am getting the following response:

{
  "severity": "permanent",
  "tags": [],
  "storage": {
    "url": "https://si.api.mailgun.net/v3/domains/mg.saasmart.com.br/messages/eyJwIjpmYWxzZSwiayI6ImRmNjI0ZTYxLTdlMTAtNDM2OC05NGZlLTdjNjU0NmNhZTcxNSIsInMiOiJjMTNlODE0MjYzIiwiYyI6InNiaWFkIn0=",
    "key": "eyJwIjpmYWxzZSwiayI6ImRmNjI0ZTYxLTdlMTAtNDM2OC05NGZlLTdjNjU0NmNhZTcxNSIsInMiOiJjMTNlODE0MjYzIiwiYyI6InNiaWFkIn0="
  },
  "delivery-status": {
    "tls": true,
    "mx-host": "mx.zoho.com",
    "attempt-no": 1,
    "description": null,
    "session-seconds": 1.996311902999878,
    "code": 541,
    "message": "541 5.4.1 Mail rejected by destination domain",
    "certificate-verified": true
  },
  "recipient-domain": "saasmart.co",
  "event": "failed",
  "campaigns": [],
  "reason": "generic",
  "user-variables": {},
  "flags": {
    "is-routed": false,
    "is-authenticated": true,
    "is-system-test": false,
    "is-test-mode": false
  },
  "log-level": "error",
  "timestamp": 1477427796.423687,
  "envelope": {
    "transport": "smtp",
    "sender": "postmaster@mg.saasmart.com.br",
    "sending-ip": "209.61.151.224",
    "targets": "julio.coutinho@saasmart.co"
  },
  "message": {
    "headers": {
      "to": "fmarcia.nascimento@gmail.com",
      "message-id": "20161025203624.11965.5253.0A1CCFF3@mg.saasmart.com.br",
      "from": "\"Sistema de Reservas Libertas\" <postmaster@mg.saasmart.com.br>",
      "subject": "Confirmação da Reserva"
    },
    "attachments": [],
    "recipients": [
      "julio.coutinho@saasmart.co",
      "fmarcia.nascimento@gmail.com",
      "reservas@amazonaspalace.com.br"
    ],
    "size": 5737
  },
  "recipient": "julio.coutinho@saasmart.co",
  "id": "xbol_i82QU-yPPbDhW3Jpw"
}