c# - "a@bbb..com"是有效的电子邮件地址吗？根据 MailAddress 类，它是

Question

为了验证电子邮件地址，我们正在转发 MailAddress Class .但是，根据 MailAddress 类，此电子邮件 a@bbb..com 地址似乎是有效的。

MSDN 指出这是有效的电子邮件地址:

The MailAddress class supports the following mail address formats:

• A simple address format of user@host. If a DisplayName is not set, this is the mail address format generated.
• A standard quoted display name format of "display name" . If a DisplayName is set, this is the format generated.
• Angle brackets are added around the User name, Host name for "display name" user@host if these are not included.
• Quotes are added around the DisplayName for display name , if these are not included.
• Unicode characters are supported in the DisplayName. property.
• A User name with quotes. For example, "user name"@host.
• Consecutive and trailing dots in user names. For example, user...name..@host.
• Bracketed domain literals. For example, .
• Comments. For example, (comment)"display name"(comment)<(comment)user(comment)@(comment)domain(comment)>(comment). Comments are removed before transmission.

取自https://msdn.microsoft.com/en-us/library/system.net.mail.mailaddress%28v=vs.110%29.aspx .

请注意，7 号项目符号与此问题很接近，但它表示连续的点可以出现在用户名中，而不是域中。

其他资源，如 http://isemail.info ( http://isemail.info/a@bbb..com ) 声明这不是有效的电子邮件地址。

您认为正确的行为应该是什么？。这是一个 poc。

//C# Example
var emailAddress = @"a@bbb..com";

Func<string,bool> validEmail = (email)=>
{
    try
    {
      var address = new System.Net.Mail.MailAddress(email);
      return true;      
    }catch (Exception ex)
    {
        return false;
    }
};

Assert.IsTrue(validEmail(emailAddress));
//using NUnit.Framework
//O2Ref:nunit.framework.dll

Answer 1

我认为(我个人借助本文档对 RFC822 的解释 https://www.cs.tut.fi/~jkorpela/rfc/822addr.html)地址

a@bbb..com

根据 RFC 822 无效特别是它的LEXICAL TOKENS定义

您将地址的域部分定义为

domain      =  sub-domain *("." sub-domain)

sub-domain  =  domain-ref / domain-literal

domain-ref  =  atom

atom        =  1*<any CHAR except specials, SPACE and CTLs>

specials    =  "(" / ")" / "<" / ">" / "@"   ;  Must be in quoted-
             /  "," / ";" / ":" / "\" / <">  ;  string, to use
             /  "." / "[" / "]"              ;  within a word.    

domain-literal =  "[" *(dtext / quoted-pair) "]"

dtext       =  <any CHAR excluding "[",     ; => may be folded
                 "]", "\" & CR, & including
                 linear-white-space>

linear-white-space =  1*([CRLF] LWSP-char)   ; semantics = SPACE
                                             ; CRLF => folding

quoted-pair =  "\" CHAR                      ; may quote any char

CHAR        =  <any ASCII character>         ; (  0-177,  0.-127.)

所以点字符是一个特殊字符，需要用引号引起来，否则它是“域”部分中定义的分隔符。

根据@dkarp:

"." 表示它是一个字面上的点，而不是另一个 ABNF 产品。所以一个domain一般是用点分隔的atom，atom至少是一个非specials字符连续。