邮件地址的问题

什么样的邮件地址才是有效的？看了Wikipedia的解释着实让人吓了一跳（留存备考）：

Valid email addresses

• niceandsimple@example.com
• very.common@example.com
• a.little.lengthy.but.fine@dept.example.com
• disposable.style.email.with+symbol@example.com
• user@[IPv6:2001:db8:1ff::a0b:dbd0]
• "much.more unusual"@example.com
• "very.unusual.@.unusual.com"@example.com
• "very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com
• 0@a
• postbox@com (top-level domains are valid hostnames)
• !#$%&'*+-/=?^_`{}|~@example.org
• "()<>[]:,;@\\\"!#$%&'*+-/=?^_`{}| ~  ? ^_`{}|~.a"@example.org
• ""@example.org

Invalid email addresses

• Abc.example.com (an @ character must separate the local and domain parts)
• Abc.@example.com (character dot(.) is last in local part)
• Abc..123@example.com (character dot(.) is double)
• A@b@c@example.com (only one @ is allowed outside quotation marks)
• a"b(c)d,e:f;g<h>i[j\k]l@example.com (none of the special characters in this local part is allowed outside quotation marks)
• just"not"right@example.com (quoted strings must be dot separated, or the only element making up the local-part)
• this is"not\allowed@example.com (spaces, quotes, and backslashes may only exist when within quoted strings and preceded by a backslash)
• this\ still\"not\\allowed@example.com (even if escaped (preceded by a backslash), spaces, quotes, and backslashes must still be contained by quotes)