Legal Hold can be used as an alternative to using third-party backup solutions since all emails are retained and cannot be deleted by the user or admin, except by retention policies.
Admins can place mailboxes on litigation hold or in-place hold. When you place content locations on hold, content is held until you remove the hold from the content location or until you delete the hold.
Litigation hold in O365 originally only existed for Exchange Online mailbox data, but has been extended to SharePoint Online, Teams, OneDrive, etc.
The user you wish to place on hold must a subscription that includes at least Exchange Online (Plan 2). This includes the following online licenses:
- Microsoft 365 E5
- Microsoft 365 E3
- Office 365 E5
- Office 365 E3
One great advantages of hold is that the user account can be deleted after they leave the company and the data will still be preserved for eDiscovery. So you won’t be burning a license for a user who does not access their mailbox any longer.
For more information about litigation or legal hold in Office 365, read In-Place Hold and Litigation Hold in Exchange Server.