Forward PMPro IPN messages from one site to another.

my_pmpro_forward_ipn.php

/**
 * Forward PMPro IPNs to another PMPro site.
 */
function my_pmpro_forward_ipn() {	
	$fp = wp_remote_post( 'https://theothersite.com/wp-admin/admin-ajax.php?action=ipnhandler', $_POST );	
}
add_action('wp_ajax_nopriv_ipnhandler', 'my_pmpro_forward_ipn', 5);
add_action('wp_ajax_ipnhandler', 'my_pmpro_forward_ipn', 5);