Hi @ninessas
What's you Exchange server version? Do you mean your event logs are cleared and you want to find 'who' deleted them?
Please correct me if I have any misunderstanding about your question. If that's the case, we could refer to the below threads which discussed the similar issues:
How to find out who deleted Event Viewer logs
Windows event logs clears or delete itself??
Audit Event logs clear Microsoft-Exchange Activemonitoring ManagedAvailability
Also check that your system logs is not being overwritten by itselft due to maximum size let's say 10 MB or so
Exchange server will not actively delete logs. If you make sure the logs was deleted, I would suggest you use other tool to monitor logs are deleted by which application.
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