Immutability is the industry-standard term for “preserving data in the system so that it is discoverable, and cannot be destroyed or altered."
With Exchange Server 2016, and Exchange Online, Microsoft enables organizations to preserve individual or all mailbox items for discovery natively, keeping those items within the Exchange infrastructure. This approach is called, In-Place hold.
One significant benefit of hold as opposed to separate, read-only storage is that items are preserved within the Exchange infrastructure, preserving more of the information including metadata and making management easier for IT admins. Users benefit because they can manage their mailboxes using the familiar Outlook interfaces. From an IT-perspective, In-Place Hold eliminates the necessity and complexity of maintaining a separate infrastructure and potentially storage for Exchange items.
Exchange gives organizations the flexibility to choose the architecture that can help meet their immutability requirements whether that is on-premises, online, or a hybrid of both, and supports the ability to store archived items in a separate physical location.
Additionally, you can use In-Place Hold to:
In the normal deleted item workflow, a mailbox item is moved to the Deletions subfolder in the Recoverable Items folder when a user permanently deletes it (Shift + Delete) or deletes it from the Deleted Items folder. A deletion policy (which is a retention tag configured with a Delete retention action) also moves items to the Deletions subfolder when the retention period expires. When a user purges an item in the Recoverable Items folder or when the deleted item retention period expires for an item, it's moved to the Purges subfolder in the Recoverable Items folder and marked for permanent deletion. It will be purged from Exchange the next time the mailbox is processed by the Managed Folder Assistant (MFA).
When a mailbox is placed on Litigation Hold, items in the Purges subfolder are preserved for the hold duration specified by the Litigation Hold. The hold duration is calculated from the original date an item was received or created, and defines how long items in the Purges subfolder are held. When the hold duration expires for an item in the Purges subfolder, the item is marked for permanent deletion and will be purged from Exchange the next time the mailbox is processed by the MFA. If an indefinite hold is placed on a mailbox, items will never be purged from the Purges subfolder.
The following illustration shows the subfolders in the Recoverable Items folders and the hold workflow process.
Contact Interlink today for help in defining your needs, which licensing options would be the best fit, and actually getting the service configured correctly to ensure the right data is being kept and deleted.