You can now set a dead-letter queue (DLQ) to an Amazon Simple Notification Service (SNS) subscription to capture undeliverable messages. Amazon SNS DLQs make your application more resilient and durable by storing messages in case your subscription endpoint becomes unreachable.

from Recent Announcements: https://aws.amazon.com/about-aws/whats-new/2019/11/amazon-sns-adds-support-for-dead-letter-queues-dlq/