[improve][doc] Default behaviour with acknowledge timeout (#18436)

Author: AlvaroStream

site2/docs/concepts-messaging.md

@@ -300,6 +300,12 @@ If batching is enabled, all messages in one batch are redelivered to the consume
 
 ### Acknowledgment timeout
 
+:::note
+
+By default, the acknowledge timeout is disabled and that means that messages delivered to a consumer will not be re-delivered unless the consumer crashes.
+
+:::
+
 The acknowledgment timeout mechanism allows you to set a time range during which the client tracks the unacknowledged messages. After this acknowledgment timeout (`ackTimeout`) period, the client sends `redeliver unacknowledged messages` request to the broker, thus the broker resends the unacknowledged messages to the consumer.
 
 You can configure the acknowledgment timeout mechanism to redeliver the message if it is not acknowledged after `ackTimeout` or to execute a timer task to check the acknowledgment timeout messages during every `ackTimeoutTickTime` period.