Disable mail queue of Informer (WP Plugin) to send all emails at once.

informer-disable-queue.php

<?php

/**
 * Plugin Name: Informer – disable mail queue
 * Description: Deactivates the queueing of mails in <em>Informer</em>
 * Author:      Inpsyde GmbH
 * Author URI:  http://inpsyde.com
 * License:     MIT
 * Plugin URI:  https://gist.github.com/dnaber-de/550520b5cdaf13987281bb159361b56f
 */

namespace Informer\DisableQueue;

add_filter( 'iac_mail_to_chunking', '__return_false' );