Comparing E-mail Address Validating Regular Expressions

It seems there is NOT a unique way of validating an email address by a simple regexp; http://stackoverflow.com/questions/201323/what-is-the-best-regular-expression-for-validating-email-addresses" From stackoverflow you arrive at different websites, among which there is http://isemail.info/about that provides a php,java and C# package to check the email. Is neat also the trick of adding a + sign to the end of your email to a website, to track if they gave the email to someone else. Nice also the quote: be conservative in what you do, be liberal in what you accept from others. So do you still think parsing an email is easy ?