add_filter( 'wp_mail', function( $args ){
	if( class_exists( 'WP_Papertrail_API'  ) ){
		WP_Papertrail_API::log(
			[
				'to' => $args[ 'to' ],
				'subject' => $args[ 'subject' ]
			]
			, 'wpmail' );
	}
	return $args;
});