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You shouldn't validate emails by regular expressions since, technically (at least according to spec)

"()<>[]:;@,\\\"!#$%&'*+-/=?^_`{}| ~ ? ^_`{}|~."@example.org

is a perfectly valid email address [1]

[1] http://en.wikipedia.org/wiki/Email_address#Valid_email_addre...

More like you shouldn't validate emails by using crappy regular expressions?

AFAIK there are regular expressions that cover all valid email addresses (and some invalid, but better than not recognizing one that is valid).

Although it gets pretty nasty: http://www.diablotin.com/librairie/autres/mre/chBB.html

But since nearly every character is valid in an email address before the @ sign (within ""), it's much easier to validate `*@thisisavaliddomain.com` and just try sending an email. The way we do it, if the user enters an email that matches our reasonably comprehensive regexp we consider it valid, if it doesn't match we send the user an email and get them to verify it with a link, that way most users don't have to go through an annoying click-and-confirm email validation but we can still catch a few edge cases of people mistyping

You shouldn't try to validate an email address by any means other than sending mail to it. If it works, it's valid.

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