public function backorder( $args ) {
		$args = wp_parse_args(
			$args,
			array(
				'product'  => '',
				'quantity' => '',
				'order_id' => '',
			)
		);

		$order = wc_get_order( $args['order_id'] );
		if (
			! $args['product'] ||
			! is_object( $args['product'] ) ||
			! $args['quantity'] ||
			! $order
		) {
			return;
		}

		$subject = sprintf( '[%s] %s', $this->get_blogname(), __( 'Product backorder', 'woocommerce' ) );
		/* translators: 1: product quantity 2: product name 3: order number */
		$message = sprintf( __( '%1$s units of %2$s have been backordered in order #%3$s.', 'woocommerce' ), $args['quantity'], html_entity_decode( wp_strip_all_tags( $args['product']->get_formatted_name() ), ENT_QUOTES, get_bloginfo( 'charset' ) ), $order->get_order_number() );

		wp_mail(
			apply_filters( 'woocommerce_email_recipient_backorder', get_option( 'woocommerce_stock_email_recipient' ), $args, null ),
			apply_filters( 'woocommerce_email_subject_backorder', $subject, $args, null ),
			apply_filters( 'woocommerce_email_content_backorder', $message, $args ),
			apply_filters( 'woocommerce_email_headers', '', 'backorder', $args, null ),
			apply_filters( 'woocommerce_email_attachments', array(), 'backorder', $args, null )
		);
	}