Amazon S3 on Outposts supports direct access for applications running outside the Outposts VPC

Amazon S3 on Outposts now supports the ability to create and access S3 objects on Outposts directly from your on-premises network. You can now configure S3 endpoints using your customer owned IP (CoIP) addresses and access your S3 objects from your on-premise network through the Outposts Local Gateway (LGW). With direct access, applications outside the Outposts Virtual Private Cloud (VPC) can now directly access data stored in S3 buckets on your Outposts. 

Source:: Amazon AWS