Python正则表达式电子邮件地址

Question

我有一组电子邮件地址，想确认它们是否是适用于GMail的有效电子邮件地址。

可能的电子邮件地址：

"[e-mail]"
"[e-mail]"
"[e-mail]"
"[e-mail]"
"patrick.o'[e-mail]" 

然而，以下内容将不是有效的电子邮件地址。

"[e-mail]"
"[e-mail]"

我所拥有的是以a-z或0-9开头的字符串，后跟零个或多个特殊字符。

re.search("^[a-z0-9]+[\.'\-]*[a-z0-9]+@(gmail|googlemail)\.com$", s)

但是它在以下位置出现故障：

"[e-mail]"

- Eamonn

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http://emailregex.com/ - tzaman

你不想让第一部分成为[a-z0-9].*[a-z0-9]吗（也要考虑大小写）？请注意，使用正则表达式验证电子邮件地址存在许多问题：https://dev59.com/uHVC5IYBdhLWcg3wtzut - jonrsharpe

目前大小写不重要。[a-z0-9].*[a-z0-9] 在“[e-mail]”上失败。Gmail链接在“[e-mail]”上失败。 - Eamonn

使用 ((^[a-z0-9])+([a-z0-9-.][a-z0-9]))+@(gmail|googlemail).com$ 已经可以正常工作。 - Eamonn

Answer 1

这是一件棘手的事情，使用正则表达式很难或不可能做到正确，因为它很快就会失控。在设计过滤器时，您必须权衡关于误报和漏报的担忧，并根据自己的喜好做出任何决定。认为这种类型的过滤器会100%工作是不正确的。 基于您的要求，您应该做出以下决策:

1. 积极过滤，并接受一些人无法收到您的电子邮件，或
2. 不进行过滤，但从邮件列表中删除反弹的地址。

再次强调，这取决于您的需求，但我建议不要过滤。即使在电子邮件声誉是一个问题的情况下，除非您向好地址和坏地址发送相等数量的电子邮件，否则这是更好的选择。

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以下几点证明了这个事实

与您发布的内容不同:

1. [e-mail] 是非法地址
2. [e-mail] 将会收到邮件。

这表明很难做到像这样的事情。并且（在我看来）您不应该尝试。即使是“简单”和“显而易见”的事情，在电子邮件的疯狂世界中通常也不是这样。

1. It's important to note that dots don't matter in gmail addresses.

   Gmail doesn't recognize dots as characters within usernames, you can add or remove the dots from a Gmail address without changing the actual destination address; they'll all go to your inbox, and only yours. In short:

   [e-mail] = [e-mail]
   [e-mail] = [e-mail]
   [e-mail] = [e-mail]
   

   A quick test on my personal email has confirmed that emails with leading or trailing dots respect this principle:

   [e-mail] = [e-mail]
   [e-mail] = [e-mail]
   [e-mail] = [e-mail]
   

   work, and are delivered.

2. You must distinguish between valid Gmail username, and valid Gmail address. They are not the same thing. Just because you cannot register with certain string for a username does not mean that putting that same string in front of @gmail.com won't deliver an email.

   Some other points:

   • Usernames must be at least 6 characters. This means [e-mail] is, in fact, an illegal address. [e-mail], etc. are also illegal according to this guideline, although "obviously legal".
   • Usernames can contain letters (a-z), numbers (0-9), dashes (-), underscores (_), apostrophes ('), and periods (.) You should allow any combination of these in the username if you decide on a regex filter. And also the plus ('+'), and probably some other characters we haven't considered.
   • There are also max-length of username, total length of address constraints, and other constraints on emails in general.
   • Plus signs are not legal parts of Gmail usernames, but can be included in gmail addresses. [e-mail] will happily be delivered to [e-mail].

- Ezra

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我其实之前不知道 Gmail 的这个特点，但是它很有趣。不过我只是以 Gmail/Google Mail 作为例子，实际上我是在写另一个网站的内容。 - Eamonn

Answer 2

请使用这个替代方案：

^[a-z0-9]+[\.'\-a-z0-9_]*[a-z0-9]+@(gmail|googlemail)\.com$

在Regex101.com上进行了测试：

- Rodrigo López