用正则表达式验证邮件地址似乎是一件简单的事情，但是如果要完美的验证一个合规的邮件地址，其实也许很复杂。
邮件地址的规范来自于 RFC 5322 。有一个网站 emailregex.com 专门列出各种编程语言下的验证邮件地址的正则表达式，其中很多正则表达式都是我听说过而从未见过的复杂——我想说，做这个网站的程序员是被邮件验证这件事伤害了多深啊！
其实，在产品环境中，一般来说并不需要这么复杂的正则表达式来做到99.99%正确。一般来说，从执行效率和测试覆盖率来说，只需要一个简单的版本即可：
/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i
那么下面我们来看看这些更严谨、更复杂的正则表达式吧：
验证邮件地址的通用正则表达式（符合 RFC 5322 标准）
(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])
由于各种语言对正则表达式的支持不同、语法差异和覆盖率不同，所以，不同语言里面的正则表达式也不同：
Python
这个是个简单的版本：
r"(^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$)"
Javascript
这个有点复杂了：
/^[-a-z0-9~!$%^&*_=+}{\'?]+(\.[-a-z0-9~!$%^&*_=+}{\'?]+)*@([a-z0-9_][-a-z0-9_]*(\.[-a-z0-9_]+)*\.(aero|arpa|biz|com|coop|edu|gov|info|int|mil|museum|name|net|org|pro|travel|mobi|[a-z][a-z])|([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(:[0-9]{1,5})?$/i
Swift
[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,6}
PHP
PHP 的这个版本就更复杂了，覆盖率就更大一些：
/^(?!(?:(?:\x22?\x5C[\x00-\x7E]\x22?)|(?:\x22?[^\x5C\x22]\x22?)){255,})(?!(?:(?:\x22?\x5C[\x00-\x7E]\x22?)|(?:\x22?[^\x5C\x22]\x22?)){65,}@)(?:(?:[\x21\x23-\x27\x2A\x2B\x2D\x2F-\x39\x3D\x3F\x5E-\x7E]+)|(?:\x22(?:[\x01-\x08\x0B\x0C\x0E-\x1F\x21\x23-\x5B\x5D-\x7F]|(?:\x5C[\x00-\x7F]))*\x22))(?:\.(?:(?:[\x21\x23-\x27\x2A\x2B\x2D\x2F-\x39\x3D\x3F\x5E-\x7E]+)|(?:\x22(?:[\x01-\x08\x0B\x0C\x0E-\x1F\x21\x23-\x5B\x5D-\x7F]|(?:\x5C[\x00-\x7F]))*\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-[a-z0-9]+)*\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-[a-z0-9]+)*)|(?:\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\]))$/iD
Perl / Ruby
对与 PHP 的版本，Perl 和 Ruby 表示不服，可以更严谨：
(?:(?:
)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[\t]))*"(?:(?:
)?[ \t])*))*@(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*)*\<(?:(?:
)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[\t])*)(?:\.(?:(?:
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)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*(?:,@(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*)(?:\.(?:(?:
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)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*)*:(?:(?:
)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*))*@(?:(?:
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)?[ \t])*))*\>(?:(?:
)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
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)?[ \t]))*"(?:(?:
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)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
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)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
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)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
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)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
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)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*(?:,@(?:(?:
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)?[ \t])*))*\>(?:(?:
)?[ \t])*)(?:,\s*(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
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)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*))*@(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*)*\<(?:(?:
)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*(?:,@(?:(?:
)?[\t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*)*:(?:(?:
)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:
)?[ \t]))*"(?:(?:
)?[ \t])*))*@(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*)(?:\.(?:(?:
)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:
)?[ \t])*))*\>(?:(?:
)?[ \t])*))*)?;\s
Perl 5.10 及以后版本
上面的版本，嗯，我可以说是天书吗？反正我是没有解读的想法了。当然，新版本的 Perl 语言还有一个更易读的版本（你是说真的么？）
/(?(DEFINE)
(?<address> (?&mailbox) | (?&group))
(?<mailbox> (?&name_addr) | (?&addr_spec))
(?<name_addr> (?&display_name)? (?&angle_addr))
(?<angle_addr> (?&CFWS)? < (?&addr_spec) > (?&CFWS)?)
(?<group> (?&display_name) : (?:(?&mailbox_list) | (?&CFWS))? ;
(?&CFWS)?)
(?<display_name> (?&phrase))
(?<mailbox_list> (?&mailbox) (?: , (?&mailbox))*)
(?<addr_spec> (?&local_part) \@ (?&domain))
(?<local_part> (?&dot_atom) | (?"ed_string))
(?<domain> (?&dot_atom) | (?&domain_literal))
(?<domain_literal> (?&CFWS)? \[ (?: (?&FWS)? (?&dcontent))* (?&FWS)?
\] (?&CFWS)?)
(?<dcontent> (?&dtext) | (?"ed_pair))
(?<dtext> (?&NO_WS_CTL) | [\x21-\x5a\x5e-\x7e])
(?<atext> (?&ALPHA) | (?&DIGIT) | [!#\$%&'*+-/=?^_`{|}~])
(?<atom> (?&CFWS)? (?&atext)+ (?&CFWS)?)
(?<dot_atom> (?&CFWS)? (?&dot_atom_text) (?&CFWS)?)
(?<dot_atom_text> (?&atext)+ (?: \. (?&atext)+)*)
(?<text> [\x01-\x09\x0b\x0c\x0e-\x7f])
(?<quoted_pair> \\ (?&text))
(?<qtext> (?&NO_WS_CTL) | [\x21\x23-\x5b\x5d-\x7e])
(?<qcontent> (?&qtext) | (?"ed_pair))
(?<quoted_string> (?&CFWS)? (?&DQUOTE) (?:(?&FWS)? (?&qcontent))*
(?&FWS)? (?&DQUOTE) (?&CFWS)?)
(?<word> (?&atom) | (?"ed_string))
(?<phrase> (?&word)+)
# Folding white space
(?<FWS> (?: (?&WSP)* (?&CRLF))? (?&WSP)+)
(?<ctext> (?&NO_WS_CTL) | [\x21-\x27\x2a-\x5b\x5d-\x7e])
(?<ccontent> (?&ctext) | (?"ed_pair) | (?&comment))
(?<comment> \( (?: (?&FWS)? (?&ccontent))* (?&FWS)? \) )
(?<CFWS> (?: (?&FWS)? (?&comment))*
(?: (?:(?&FWS)? (?&comment)) | (?&FWS)))
# No whitespace control
(?<NO_WS_CTL> [\x01-\x08\x0b\x0c\x0e-\x1f\x7f])
(?<ALPHA> [A-Za-z])
(?<DIGIT> [0-9])
(?<CRLF> \x0d \x0a)
(?<DQUOTE> ")
(?<WSP> [\x20\x09])
)
(?&address)/x
Ruby (简单版)
Ruby 表示，其实人家还有个简单版本：
/\A([\w+\-].?)+@[a-z\d\-]+(\.[a-z]+)*\.[a-z]+\z/i
.NET
这样的版本谁没有啊——.NET 说：
^\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$
grep 命令
用 grep 命令在文件中查找邮件地址，我想你不会写个若干行的正则表达式吧，意思一下就行了：
$ grep -E -o "\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b" filename.txt
SQL Server
在 SQL Server 中也是可以用正则表达式的，不过这个代码片段应该是来自某个产品环境中的，所以，还体贴的照顾了那些把邮件地址写错的人：
select email
from table_name where
patindex ('%[ &'',":;!+=\/()<>]%', email) > 0 -- Invalid characters
or patindex ('[@.-_]%', email) > 0 -- Valid but cannot be starting character
or patindex ('%[@.-_]', email) > 0 -- Valid but cannot be ending character
or email not like '%@%.%' -- Must contain at least one @ and one .
or email like '%..%' -- Cannot have two periods in a row
or email like '%@%@%' -- Cannot have two @ anywhere
or email like '%.@%' or email like '%@.%' -- Cannot have @ and . next to each other
or email like '%.cm' or email like '%.co' -- Camaroon or Colombia? Typos.
or email like '%.or' or email like '%.ne' -- Missing last letter
Oracle PL/SQL
这个是不是有点偷懒？尤其是在那些“复杂”的正则表达式之后：
SELECT email
FROM table_name
WHERE REGEXP_LIKE (email, '[A-Z0-9._%-]+@[A-Z0-9._%-]+\.[A-Z]{2,4}');
MySQL
好吧，看来最后也一样懒：
SELECT * FROM `users` WHERE `email` NOT REGEXP '^[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$';
那么，你有没有关于验证邮件地址的正则表达式分享给大家？
