大多数情况下，我们的邮件到达时没有问题或怪癖，但为什么有些邮件到达时会以毫无意义的字符串作为标题？今天的超级用户问答帖子回答了一位困惑的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

照片由Judith E.Bell（Flickr）提供。

问题

超级用户读者dpdt想知道他为什么收到一封带有荒谬标题的电子邮件：

I recently received an email with the following title:

Thinking that it might be malware, I ran a check with Malwarebytes, but it came up clean. Is there any legitimate reason for the title being a n***ensical string of characters?

为什么有些电子邮件的标题是荒谬的字符串？

答案

超级用户贡献者user313114为我们提供了答案：

What you have is some header text encoded with a failed attempt at RFC 2047.

RFC 2047 is the standard governing the embedding of non-ASCII characters in email headers. It says that headers which do not comply (exactly) with the RFC 2047 standard should be displayed as-is rather than any decoding being attempted. So your email software is seeing the bad header and displaying it “correctly” (as required by the standard).

No mainstream software flouts RFC 2047 so badly as that, so it is probably coming from some dodgy bulk mailing software. The software is making encoded words too long (the line length limit is 76 characters), which is forbidden (RFC 2047 says “MUST NOT”).

Despite being too long, it can be decoded manually. It looks like some sort of recruiter spam:

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