forms - 电子邮件地址中允许使用哪些字符？

Question

我不是在询问完整的电子邮件验证。

我只想知道电子​​邮件地址的用户名和服务器部分允许使用哪些字符。这可能过于简单化，也许电子邮件地址可以采用其他形式，但我不在乎。我只询问这个简单的形式:user-name@server(例如 wild.wezyr@best-server-ever.com)以及两个部分中允许的字符。

Answer 1

参见RFC 5322: Internet Message Format并且，在较小程度上，RFC 5321: Simple Mail Transfer Protocol .

RFC 822还涵盖电子邮件地址，但主要涉及其结构:

 addr-spec   =  local-part "@" domain        ; global address     
 local-part  =  word *("." word)             ; uninterpreted
                                             ; case-preserved
 
 domain      =  sub-domain *("." sub-domain)     
 sub-domain  =  domain-ref / domain-literal     
 domain-ref  =  atom                         ; symbolic reference

像往常一样，维基百科有一个不错的 article on email addresses :

The local-part of the email address may use any of these ASCII characters:

• uppercase and lowercase Latin letters A to Z and a to z;
• digits 0 to 9;
• special characters !#$%&'*+-/=?^_`{|}~;
• dot ., provided that it is not the first or last character unless quoted, and provided also that it does not appear consecutively unless quoted (e.g. John..Doe@example.com is not allowed but "John..Doe"@example.com is allowed);
• space and "(),:;<>@[\] characters are allowed with restrictions (they are only allowed inside a quoted string, as described in the paragraph below, and in addition, a backslash or double-quote must be preceded by a backslash);
• comments are allowed with parentheses at either end of the local-part; e.g. john.smith(comment)@example.com and (comment)john.smith@example.com are both equivalent to john.smith@example.com.

除了 ASCII 字符外，as of 2012您可以使用国际 characters above U+007F ，编码为 UTF-8，如 RFC 6532 spec 中所述。并在 Wikipedia 上进行了解释。请注意，截至 2019 年，这些标准仍标记为“提议”，但正在缓慢推出。此规范中的更改本质上添加了国际字符作为有效的字母数字字符(atext)，而不影响允许和限制的特殊字符(例如 !#)的规则。和@: .

有关验证，请参阅Using a regular expression to validate an email address .

domain部分定义as follows :

The Internet standards (Request for Comments) for protocols mandate that component hostname labels may contain only the ASCII letters a through z (in a case-insensitive manner), the digits 0 through 9, and the hyphen (-). The original specification of hostnames in RFC 952, mandated that labels could not start with a digit or with a hyphen, and must not end with a hyphen. However, a subsequent specification (RFC 1123) permitted hostname labels to start with digits. No other symbols, punctuation characters, or blank spaces are permitted.