function validEmail(email) {
    if (email=="" || email== null) {
        return false;
    } else {
        var emailReg = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,6}|[0-9]{1,3})(\]?)$/; // valid
        if (!emailReg.test(email)) { // if syntax is valid
            return false;
        }
        return true;
    }
}