It is not using Mailgun API, only PHP curl

All receipts are hidden, so they don't see each other emails

No namespace, no composer, just 1 file ready to use.

1. add this file "send_mailgun_batch.php"; your PHP project
2. require_once "send_mailgun_batch.php";
3. change $domain and $mailgun_api_key
4. Call this function send_mailgun_batch($emails_to_send_array, $subject, $message);
5. If success you should see a message "Queued. Thank you."