Who is this article for?

Admins who want to understand the dead letter queue.

Administrator permissions are required.

The dead letter queue is a failsafe mechanism in Mail Manager Enterprise that captures email save requests that have exceeded the retry limit, allowing administrators to investigate critical system issues.

Processing email save requests

Mail Manager Enterprise uses Azure Service Bus queues to asynchronously process save requests. This architecture provides a layer of resiliency by guaranteeing retries on failed attempts up to a defined limit, allowing the service to complete its work even when temporary issues occur.

Understanding what happens when retry limits are reached

When a save request fails repeatedly and reaches the retry attempt limit, Azure Service Bus stops processing it. At this point, the dead lettering framework takes over.

Dead lettering is an opt-in feature within Azure Service Bus that uses a separate queue to capture failed messages. When a save attempt reaches the retry limit, Service Bus automatically places the message on this dead letter queue.

Understanding how dead letter messages are handled

Mail Manager Enterprise monitors the dead letter queue and processes messages differently from standard save requests. When a message appears on the dead letter queue, the system sends an email notification to administrators, alerting them that investigation is required.

Note: Messages reaching the dead letter queue are extremely rare and typically indicate a serious system issue that requires immediate attention.