Understanding Litigation Hold in Microsoft Exchange: A Complete Guide to Mailbox Preservation


In today's regulatory environment, organizations must be prepared to preserve electronic communications for legal discovery and compliance purposes. Microsoft Exchange Server offers a powerful feature called Litigation Hold that helps organizations meet these requirements by preserving all mailbox content, including deleted and modified items.

What is Litigation Hold?


Litigation Hold is a feature in Exchange Server (2016, 2019, and Microsoft 365) that preserves all mailbox content when legal or regulatory requirements demand it. When you place a mailbox on Litigation Hold, the system preserves:

- All mailbox items, including deleted messages
- Original versions of modified items
- Items in the user's archive mailbox (if enabled)
- Content for a specified period or indefinitely

All preserved items remain searchable through In-Place eDiscovery, making it easy to locate specific information when needed for legal proceedings or compliance audits.

Key Features and Considerations

Preservation Period


Organizations can configure Litigation Hold in two ways:
  1. Indefinite hold: Items are preserved until the hold is explicitly removed
  2. Duration-based hold: Items are preserved for a specific number of days (calculated from when the item was received or created)

Storage Requirements


The Litigation Hold feature uses the Recoverable Items folder in each mailbox to store preserved content. Key storage considerations include:

- Default size: 30 GB
- Separate storage limit (doesn't count toward mailbox quota)
- Can grow quickly depending on email volume and retention duration
- Requires regular monitoring to ensure quotas aren't exceeded

Microsoft recommends monitoring mailboxes on Litigation Hold weekly to ensure they don't reach the limits of the Recoverable Items quotas.

Activation Timeline


Important: The Litigation Hold setting may take up to 60 minutes to take effect after configuration.

How to Implement Litigation Hold

Using Exchange Admin Center (EAC)

  1. Navigate to Recipients > Mailboxes
  2. Select the target mailbox and click Edit
  3. Go to Mailbox features
  4. Under Litigation hold: Disabled, click Enable
  5. Configure optional settings:
- Duration: Specify hold period in days (leave blank for indefinite)
- Note: Message displayed to users in Outlook
- URL: Link to additional information about the hold

Using PowerShell


For single mailbox (indefinite hold): 
powershell


Set-Mailbox [email protected] -LitigationHoldEnabled $true


For single mailbox with duration: 
powershell


Set-Mailbox [email protected] -LitigationHoldEnabled $true -LitigationHoldDuration 2555


For all mailboxes in organization: 
powershell


Get-Mailbox -ResultSize Unlimited -Filter "RecipientTypeDetails -eq 'UserMailbox'" | Set-Mailbox -LitigationHoldEnabled $true -LitigationHoldDuration 365

How Litigation Hold Works


Understanding the workflow helps administrators manage the feature effectively:
  1. Normal deletion: When users delete items (Shift+Delete or empty Deleted Items), items move to the Deletions subfolder in Recoverable Items
  2. Retention policies: Deletion policies move expired items to the Deletions subfolder
  3. Purge process: When users purge items or retention expires, items move to the Purges subfolder
  4. Litigation Hold protection: Items in the Purges subfolder are preserved for the configured hold duration
  5. Final deletion: Only after the hold duration expires (or hold is removed) are items permanently deleted by the Managed Folder Assistant

Archive Mailbox Consideration


When you place a user's primary mailbox on Litigation Hold, the archive mailbox is automatically placed on hold as well. This ensures complete preservation of all user communications.

Enterprise-Wide Implementation Best Practices


Organizations implementing Litigation Hold across all mailboxes should consider:

Scalability Challenges


- New mailboxes: The hold command only affects existing mailboxes. Run the command regularly or as a scheduled task to include new mailboxes
- Storage planning: Plan for adequate storage in Exchange 2016/2019 environments, as preservation significantly impacts mailbox sizes
- Monitoring: Use Get-MailboxFolderStatistics cmdlet to track Recoverable Items folder growth

Targeted Holds


Instead of holding all mailboxes, organizations can use recipient filters to target specific groups:

By department: 
powershell


Get-Recipient -RecipientTypeDetails UserMailbox -ResultSize unlimited -Filter 'Department -eq "HR"'


By location: 
powershell


Get-Recipient -RecipientTypeDetails UserMailbox -ResultSize unlimited -Filter 'PostalCode -eq "98052"'


By custom attribute: 
powershell


Get-Mailbox -RecipientTypeDetails UserMailbox -ResultSize unlimited -Filter 'CustomAttribute15 -eq "OneYearLitigationHold"'

Verification and Management

Verify Litigation Hold Status


Via EAC:
- Navigate to the mailbox properties
- Click Mailbox features
- Check Litigation hold status
- Click View details for hold configuration and history

Via PowerShell: 
powershell


Get-Mailbox | Format-List LitigationHold*

Remove Litigation Hold


When legal requirements no longer apply: 
powershell


Set-Mailbox [email protected] -LitigationHoldEnabled $false

Compliance and Legal Considerations


Litigation Hold is essential for organizations that need to:

- Comply with legal discovery requests
- Meet regulatory compliance requirements
- Preserve evidence for litigation
- Maintain audit trails of electronic communications

The feature ensures that even if users delete items or modify messages, the original content remains available for eDiscovery searches and legal review.

Conclusion


Litigation Hold is a critical feature for organizations with legal preservation requirements. While the feature is powerful and comprehensive, it requires careful planning around storage capacity, ongoing monitoring, and clear processes for when holds should be applied and removed.

By understanding how Litigation Hold works and following Microsoft's best practices, organizations can ensure they meet their legal obligations while managing the operational impact on their Exchange environment.
Source: Microsoft Learn - Place a mailbox on Litigation Hold