Method isEmailAddress

/**
 * Verifies that the string is in a proper email address format.
 *
 * @param   string  $email  String to be verified.
 *
 * @return  boolean  True if string has the correct format; false otherwise.
 *
 * @since   1.7.0
 */
public static function isEmailAddress($email)
{
    // Split the email into a local and domain
    $atIndex = strrpos($email, '@');
    $domain = substr($email, $atIndex + 1);
    $local = substr($email, 0, $atIndex);
    // Check Length of domain
    $domainLen = \strlen($domain);
    if ($domainLen < 1 || $domainLen > 255) {
        return false;
    }
    /*
     * Check the local address
     * We're a bit more conservative about what constitutes a "legal" address, that is, a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-
     * The first and last character in local cannot be a period ('.')
     * Also, period should not appear 2 or more times consecutively
     */
    $allowed = "a-zA-Z0-9.!#\$%&'*+\\/=?^_`{|}~-";
    $regex = "/^[{$allowed}][\\.{$allowed}]{0,63}\$/";
    if (!preg_match($regex, $local) || substr($local, -1) === '.' || $local[0] === '.' || preg_match('/\\.\\./', $local)) {
        return false;
    }
    // No problem if the domain looks like an IP address, ish
    $regex = '/^[0-9\\.]+$/';
    if (preg_match($regex, $domain)) {
        return true;
    }
    // Check Lengths
    $localLen = \strlen($local);
    if ($localLen < 1 || $localLen > 64) {
        return false;
    }
    // Check the domain
    $domain_array = explode('.', $domain);
    $regex = '/^[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)*$/';
    foreach ($domain_array as $domain) {
        // Convert domain to punycode
        $domain = PunycodeHelper::toPunycode($domain);
        // Must be something
        if (!$domain) {
            return false;
        }
        // Check for invalid characters
        if (!preg_match($regex, $domain)) {
            return false;
        }
        // Check for a dash at the beginning of the domain
        if (strpos($domain, '-') === 0) {
            return false;
        }
        // Check for a dash at the end of the domain
        $length = \strlen($domain) - 1;
        if (strpos($domain, '-', $length) === $length) {
            return false;
        }
    }
    return true;
}