Add Custom Validation Rule to CF7

Adds a custom validation rule to Contact Form 7

PHP

function custom_email_validation_filter($result, $tag) {
    $type = $tag['type'];
    $name = $tag['name'];
    if ($type == 'email*' && $_POST[$name] != '') {
        if (strpos($_POST[$name], 'example.com') !== false) {
            $result->invalidate($tag, "We don't accept example.com email addresses");
        }
    }
    return $result;
}
add_filter('wpcf7_validate_email*', 'custom_email_validation_filter', 10, 2);
add_filter('wpcf7_validate_email', 'custom_email_validation_filter', 10, 2);