关于Yahoo发邮件失败，Error: "421 4.7.0 [XXX] Messages from x.x.x.x temporarily deferred due to user complaints - 4.16.55.1" when sending email to Yahoo

Yahoo返回的消息如下：
4.7.0 [TSS04] Messages from 104.130.96.10 temporarily deferred due to user complaints - 4.16.55.1; see https://help.yahoo.com/kb/postmaster/SLN3434.html

mailgun给的答复：

The error that you are seeing is ESP throttling, and this occurs whenever the recipient's email service provider (ESP) has received a large number of emails from a specific IP in a short amount of time. Due to this, they will not accept messages for a certain period of time (usually an hour) until they have processed all the emails from the original batch sent. ESP throttling is a common occurrence in the email world, and we're one of the few providers that actually show these messages in the email logs. 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.
 

您看到的错误是ESP节流，每当收件人的电子邮件服务提供商（ESP）在短时间内从特定IP接收到大量电子邮件时，就会发生这种情况。由于这个原因，他们在一段时间（通常是一个小时）内不会接受邮件，直到他们处理完了从原始批量发送的所有电子邮件。ESP节流在电子邮件世界中很常见，我们是少数几个在电子邮件日志中实际显示这些消息的提供者之一。

“4xx”的错误代码表明这是一个软的、暂时的反弹。每当我们试图传递消息并且接收方服务器返回软弹跳时，我们将在以下间隔内重试传递最多8小时：10分钟、10分钟、15分钟、30分钟、1小时、2小时和4小时。不幸的是，这无法调整，在我们的环境中是硬编码的。

-----------------

mailgun针对此类邮箱试图重新发送

Yahoo给的建议:
1.错误是暂时的。我们建议您在遇到错误后4小时重试发送电子邮件。
2.如果您不是相关邮件服务器的管理员，我们建议您直接与管理员联系以讨论错误。
3.如果您是邮件内容和邮件策略的管理员，并且您已部署了重大更改，或者您收到此错误的时间超过48小时，我们会要求您查看外发邮件以查找令人反感的内容或做法。
4.请参阅我们针对批量邮件发件人和邮件管理员的建议指南，并注意我们不会透露有关我们的过滤实践的更多信息。