Google Vault is a premium service with GSuite that keeps a searchable log of all emails and files even when deleted.
This is useful for system admins that may need to search for content from deleted files for compliance or investigation issues and is somewhat of a legal obligation for businesses with best-practice record-keeping expectations.
Given that deleting stuff is usually intended to recover disk-space, it would make sense for the storage of this to be to an S3 compatible service like Backblaze or Wasabi that has features for storing historic versions of files regardless of changes or deletions.
This is probably the only thing stopping me migrating all email services over to a Cloudron setup for some main domains now.
I can see Kibana making a good frontend for something like this if there isn't already an App or tool to do this sort of thing specifically.
Certainly a good box to be able to tick for more compliance and enterprise orientated type clients.