电子邮件地址是否区分大小写? [英] Are email addresses case sensitive?

问题描述

我已经读过电子邮件的标准第一部分区分大小写，但是我尝试将电子邮件发送到 [e-mail], [e-mail] 和 [e-mail] - 在每种情况下都已到达.

I've read that by standard first part of e-mail is case sensitive, however I've tried to send e-mail to [e-mail], [e-mail] and [e-mail] - it has arrived in each case.

邮件服务器如何处理用户名?是否有可能错过案例并且该消息不会被传递?使用与注册时填写的完全相同的字母大小写真的很重要吗?

How do mail servers handles usernames? Is it possible to miss with case and that message wouldn't be delivered? Is it really very important to use exactly same letter case, as was written while registering when giving your e-mail address?

推荐答案

来自 RFC 5321，第 2.3.11 节:

标准邮箱命名约定定义为本地部分@域"；当代用法允许更广泛的一组应用程序比简单的用户名"更重要.因此，并且由于中间宿主试图解决问题的悠久历史通过修改它们来优化传输，本地部分必须是仅由主机中指定的主机解释和分配语义地址的域部分.

The standard mailbox naming convention is defined to be "local-part@domain"; contemporary usage permits a much broader set of applications than simple "user names". Consequently, and due to a long history of problems when intermediate hosts have attempted to optimize transport by modifying them, the local-part MUST be interpreted and assigned semantics only by the host specified in the domain part of the address.

是的，@"之前的部分可能区分大小写，因为它完全在主机系统的控制之下.但实际上，并没有广泛使用的邮件系统根据大小写区分不同的地址.

So yes, the part before the "@" could be case-sensitive, since it is entirely under the control of the host system. In practice though, no widely used mail systems distinguish different addresses based on case.

@ 符号后面的部分是域，根据 RFC 1035，第 3.1 节，

The part after the @ sign however is the domain and according to RFC 1035, section 3.1,

名称服务器和解析器必须以不区分大小写的方式比较 [域]"

"Name servers and resolvers must compare [domains] in a case-insensitive manner"

简而言之，您可以安全地将电子邮件地址视为不区分大小写.

In short, you are safe to treat email addresses as case-insensitive.

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