通过 Mailgun 发送错误：“421 语法错误”

Question

我正在通过 node.js 应用程序向 Mailgun 发送电子邮件。我不断收到这些 421 语法错误消息。有时消息确实会通过，这是一条消息的历史记录：

Date/Time   Summary 
2015-05-07 16:14    Delivered: sender → recipient 'You have a new notification' 
2015-05-07 15:14    Will retry in 3600 seconds: sender → recipient 'You have a new notification' Server response: 421 421 Syntax error  
2015-05-07 14:43    Will retry in 1800 seconds: sender → recipient  'You have a new notification' Server response: 421 421 Syntax error 
2015-05-07 14:28    Will retry in 900 seconds: sender → recipient  'You have a new notification' Server response: 421 421 Syntax error  
2015-05-07 14:18    Will retry in 600 seconds: sender → recipient  'You have a new notification' Server response: 421 421 Syntax error  
2015-05-07 14:18    Accepted: sender → recipient  'You have a new notification'

*电子邮件地址已编辑。

以下是日志针对 421 错误的说明：

{
  "severity": "temporary",
  "tags": [],
  "delivery-status": {
    "retry-seconds": 600,
    "message": "421 Syntax error",
    "code": 421,
    "description": null,
    "session-seconds": 0.16810393333435059
  },
  "envelope": {
    "transport": "smtp",
    "sender": sender,
    "sending-ip": "184.173.153.222",
    "targets": recipient
  },
  "recipient-domain": domain,
  "id": "TdCQ8omOSwqj_zYq18CBdQ",
  "campaigns": [],
  "reason": "generic",
  "user-variables": {},
  "flags": {
    "is-routed": null,
    "is-authenticated": true,
    "is-system-test": false,
    "is-test-mode": false
  },
  "log-level": "warn",
  "timestamp": 1431029901.450764,
  "message": {
    "headers": {
      "to": recipient,
      "message-id": "20150507201819.16176.81911@mailgundomain",
      "from": sender,
      "subject": "You have a new notification"
    },
    "attachments": [],
    "recipients": [
      recipient
    ],
    "size": 1036
  },
  "recipient": recipient,
  "event": "failed"
}

我刚开始使用 Mailgun，我正在构建电子邮件 RAW（headers 和所有）。 421 应该是网络错误...所以 'Syntax error' 对我来说没有意义。

有些消息通过得很好，但我确实有很多消息正在重试。

有什么想法吗？

谢谢

Answer 1

我在 Mailgun 支持下创建了工单，他们很快帮我找到了答案：

The error that you are seeing is due to the recipient's server either 
1). throttling emails sent from your domain which is also known as ESP
throttling, 2) grey-listing of the IP in which the recipient server will
first verify that the sending server is not sending spam before allowing
delivery, or 3) a local server issue may have occurred such as the server
being offline or misconfigured.

The error code of "4xx" indicates that this is a soft, temporary bounce.
Whenever we attempt to deliver a message and the recipient server returns a
soft bounce, we will retry delivery for up to 8 hours in the following
intervals: 10 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hour
and 4 hours. Unfortunately this cannot be adjusted and is hard coded in our
environment.

我咨询了我们的管理员，我们为邮件服务器启用了一些反垃圾邮件功能。我们将其关闭，不再出现“421 语法错误”。

谢谢

通过 Mailgun 发送错误：“421 语法错误”

Errors sending through Mailgun: '421 Syntax error'

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