问题描述
我的网络应用程序相当频繁地发送电子邮件，它会发送3种电子邮件：由用户启动，以响应系统中的事件，并自动响应应用程序收到的电子邮件。
My web application sends email fairly often, and it sends 3 kinds of emails: initiated by user, in response to an event in the system, and in automatic response to an email received by the application.
我想确保第三种类型的电子邮件不会陷入无休止的自动回复循环中。目前，我使用标题：
I would like to make sure that the third type of email does not get stuck in an endless loop of auto-responders talking to each other. Currently, I use the header:
Precedence: junk
但雅虎邮件正在将这些邮件视为垃圾邮件。这显然不是很理想，因为我们希望SOMEBODY能够阅读我们的自动回复并对此做出决定，而不是外出回复。
but Yahoo! mail is treating these messages as spam. This is obviously not ideal, because we would like SOMEBODY to read our auto-response and make a decision on it, just not an out-of-office reply.
发送电子邮件的最佳方式是什么，而不触发垃圾过滤器或自动回复？
Precedence: junk?
Precedence: bulk?
Precedence: list?
X-Priority: 2?
推荐答案
不鼓励使用优先级标题。正如你所注意到的，许多客户将只是过滤掉（特别是优先级：垃圾品种）。使用空路径避免自动响应策略可能会更好：
RFC 2076 discourages the use of the precedence header. as you have noted, many clients will just filter that off (especially the precedence: junk variety). it may be better to use a null path to avoid auto responder wars:
Return-Path: <>
最终，您可以优先考虑这一点，但这似乎违背了标题。我建议只使用返回路径头，并避免优先。在某些情况下，您可能必须以某种方式写入您的应用程序中的自动回复（避免进入响应者战争），但我不记得使用适当的返回路径发生这种情况。 （大部分自动回复战争我记得要处理的都是电子邮件格式错误的结果）
Ultimately you could use priority to try to get around this, but this seems like going against the spirit of the header. i'd suggest just using the return-path header for this, and avoiding precedence. in some cases you may have to write in some way to drop auto-responders in your application (to avoid getting into a responder war), but i can't remember a situation in which this happened using an appropriate return-path. (most auto responder wars i recall having to deal with were the result of very badly formed emails)
注意：返回路径标头是通知的目的地（反弹，延迟传递等），并在 - 因为SMTP是必需的。这也是减少不良邮件的一种方法（理论上所有的好邮件都会设置一个合适的返回路径）。
Note: the Return-Path header is, in short, the destination for notifications (bounces, delay delivery, etc...), and is described in RFC 2821 -- because it's required by SMTP. It's also one method to drop bad mail (as theoretically all good mail will set an appropriate return-path).
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