Even if it's just a regex, handling the fully-general case is surprisingly complex: http://stackoverflow.com/questions/201323/using-a-regular-expression-to-vali

Even if it's just a regex, handling the fully-general case is surprisingly complex: http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address/1917982#1917982 http://stackoverflow.com/questions/201323/using-a-regular-ex... This doesn't even count domain validation, what with new TLDs coming online constantly, etc.