# Capturing problematic messages in Amazon SQS
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To capture all messages that can't be processed, and to collect accurate CloudWatch metrics, configure a [dead-letter queue](sqs-dead-letter-queues.md).
+ The redrive policy redirects messages to a dead-letter queue after the source queue fails to process a message a specified number of times.
+ Using a dead-letter queue decreases the number of messages and reduces the possibility of exposing you to *poison pill* messages (messages that are received but can't be processed).
+ Including a poison pill message in a queue can distort the [`ApproximateAgeOfOldestMessage`](sqs-available-cloudwatch-metrics.md) CloudWatch metric by giving an incorrect age of the poison pill message. Configuring a dead-letter queue helps avoid false alarms when using this metric.