Final answer:
Amazon SQS handles unprocessable messages by using a dead-letter queue system where messages that fail to process after a certain number of retries are sent to a secondary queue for further analysis or manual processing.
Step-by-step explanation:
When Amazon Simple Queue Service (Amazon SQS) encounters messages that can't be processed, it manages them through a process known as dead-letter queuing. When a message is received but is not successfully processed, it is returned to the queue to be retried. Amazon SQS offers a redrive policy where you can set the maximum number of retries before a message is sent to a specified dead-letter queue (DLQ). A DLQ is a secondary queue where messages that have repeatedly failed can be isolated and analyzed or manually processed.
Moreover, once in the dead-letter queue, system administrators or developers can take action by analyzing the reason messages couldn't be processed and take appropriate corrective measures. This feature helps to maintain the integrity of the message processing system and avoid continuously retrying messages that will never succeed due to issues such as message corruption or an unsupported format.