gmail（mailgun）-> daum（hanmail）邮件发送重复发货

Question

使用Mailgun服务从gmail发送邮件时，将正常接收发送到naver，gmail，lineworks等的邮件。但是，如果我将其发送到hanmail，我会收到很多次。邮件发送日志如下。我发送了同样的问题，DAUM和GMAIL。

{
"tags": [],
"envelope": {
    "sender": "kiwanpark@s2d5.com",
    "transport": "smtp",
    "targets": "kimpaul35@hanmail.net"
},
"storage": {
    "url": "https://sw.api.mailgun.net/v3/domains/s2d5.com/messages/eyJwIjp0cnVlLCJrIjoiM2QwN2E2Y2YtZTViYi00OTRlLWJjOGEtZDVkMTRlY2VhYzJlIiwicyI6ImE4ZDg2ZjYxZjQiLCJjIjoiYmlndGFua2IifQ==",
    "key": "eyJwIjp0cnVlLCJrIjoiM2QwN2E2Y2YtZTViYi00OTRlLWJjOGEtZDVkMTRlY2VhYzJlIiwicyI6ImE4ZDg2ZjYxZjQiLCJjIjoiYmlndGFua2IifQ=="
},
"log-level": "info",
"id": "DRcUt8G9Trm9A8etbo4FIQ",
"campaigns": [],
"method": "smtp",
"user-variables": {},
"flags": {
    "is-routed": false,
    "is-authenticated": true,
    "is-system-test": false,
    "is-test-mode": false
},
"recipient-domain": "hanmail.net",
"timestamp": 1537528086.529777,
"message": {
    "headers": {
        "to": "kimpaul35@hanmail.net",
        "message-id": "CACd+hUckHzBYsi0Vho2nVT3NusB4JckqTq1KdrHD-VKRVS1dkg@mail.gmail.com",
        "from": "박기완 <kiwanpark@s2d5.com>",
        "subject": "[input] 2018 0921 2000 버전"
    },
    "attachments": [
        {
            "size": 19350112,
            "content-type": "application/vnd.android.package-archive",
            "filename": "input-app-debug-20180921-2000.apk"
        }
    ],
    "size": 19352930
},
"recipient": "kimpaul35@hanmail.net",
"event": "accepted"

}

ps。当时，曾有18次临时失败。那是原因吗？