Which statement about the Message Service (MS) event notification is correct?

The statement regarding events being retried based on the specified policy is accurate because Message Service (MS) in Alibaba Cloud offers a robust delivery mechanism that includes retry policies for event notifications. When an event is published and a consumer fails to process it successfully, the service can automatically retry delivering that message based on predefined settings. This ensures that transient failures do not lead to data loss and that messages are eventually delivered once the issue is resolved.

In contrast, the other options present characteristics that do not align with the behavior of the Message Service. For instance, messages in MS typically do not remain in the system indefinitely, as they usually have a retention policy that defines how long a message can stay in the queue or topic before being discarded. Moreover, HTTP Server is indeed a valid consumer type for event notifications, which allows consumers to receive messages over HTTP. Lastly, messages sent through Message Service can be delivered to multiple consumers concurrently, provided they are set up to receive them, supporting various application architectures and enhancing flexibility in message processing.