When queue or topic has “Requires duplicate detection” turned on, it will detect and discard duplicate message. Duplicated are checked in all messages received within “Duplicate detection time window”, which is by default 10 minutes. Duplicates are determined by comparing MessageId, and if queue is partitioned or with sessions - PartitionKey and SessionID.
If user performs an action which would result in sending a message to a queue with “duplicate detection” turned on like edit, requeue, paste, etc, QueueExplorer will display a warning about potential message loss and offer to replace MessageIDs with auto-generated ones.
Please note that in some cases MessageID should not be modified (or auto-generated) because applications use it to pass some business data. In these cases, MessageIDs should be kept as is. It’s up to user to decide whether MessageIDs can be changed.