Old Post Notification - Change Post Types

functions.php

<?php

/**
 * Add Article as Post Type for Old Post Notification
 *
 * @param array $post_types
 * @return array
 */
function be_post_types_for_notification( $post_types ) {
	$post_types[] = 'article';
	return $post_types;
}

add_filter( 'old_post_notification_post_types', 'be_post_types_for_notification' );