How to put a mailbox on litigation hold

Putting a mailbox on litigation hold in Exchange Online is a single setting that preserves every item in the mailbox — including things the user deletes or edits from now on — until the hold is released or its duration expires. It takes effect within about an hour, needs an Exchange Online Plan 2 (or Archiving add-on) licence on the mailbox, and is the right tool when legal says "preserve everything for this person, starting now".

The broader picture — archiving, the Recoverable Items folder, and how holds interact with retention policies — is in Exchange Online archiving and litigation hold. When the request is case-shaped rather than person-shaped, use Purview eDiscovery holds instead.

Prerequisites

• Exchange Administrator, or the Legal Hold role via a custom Exchange role group. Compliance Administrator in Purview can also apply holds through eDiscovery but not this per-mailbox switch.
• The mailbox licensed with Exchange Online Plan 2 or Exchange Online Archiving; the setting is greyed out otherwise.
• A ticket or legal reference to record in the hold's comment field; you will be asked years later why this hold exists.
• For a leaver: keep the licence and the account. A hold on a mailbox whose account is deleted becomes an inactive mailbox, which is fine and intended, but only if the hold was in place before deletion.

Steps

1. Confirm the licence

Connect-ExchangeOnline
Get-Mailbox user@contoso.com | Format-List RecipientTypeDetails,PersistedCapabilities,LitigationHoldEnabled

PersistedCapabilities should include BPOS_S_Enterprise (Plan 2) or BPOS_S_Archive/BPOS_S_ArchiveAddOn. If not, assign the licence first and wait for the mailbox to reflect it.

2. Enable the hold

Exchange admin center: Recipients → Mailboxes → the mailbox → Others → Manage litigation hold → Turn on. Enter the duration in days (leave blank for indefinite), a note for the user (optional), and a URL to your legal-hold policy page (optional). Save.

Or:

Set-Mailbox user@contoso.com -LitigationHoldEnabled $true -LitigationHoldDuration 2555 `
  -LitigationHoldOwner legal@contoso.com -Comment "Matter 2026-014, per Legal 2026-09-03"

Omit -LitigationHoldDuration for indefinite. The comment and owner are visible in Get-Mailbox and are how the next admin finds out who to ask.

3. Bulk holds

For a list of users:

Import-Csv .\custodians.csv | ForEach-Object {
  Set-Mailbox $_.UPN -LitigationHoldEnabled $true -Comment "Matter 2026-014"
}

If there are more than a handful of custodians and the matter is a real case, an eDiscovery (Premium) case hold is easier to manage and release together.

4. Check the archive and quota

A held mailbox keeps deleted items in Recoverable Items, which has its own quota (100 GB when hold is enabled). Heavy mailboxes benefit from enabling the archive and auto-expanding archiving so Recoverable Items overflow has somewhere to go: Enable-Mailbox user@contoso.com -Archive then Enable-Mailbox user@contoso.com -AutoExpandingArchive.

Verify

• Get-Mailbox user@contoso.com | fl LitigationHoldEnabled,LitigationHoldDate,LitigationHoldOwner,LitigationHoldDuration shows the hold and its start date. Allow up to 60 minutes after enabling.
• Delete a test item as the user, empty Deleted Items, then search Get-RecoverableItems -Identity user@contoso.com — the item is still there.
• The tenant audit checklist should include a periodic Get-Mailbox -Filter {LitigationHoldEnabled -eq $true} review so holds do not outlive their matters.

Roll back

Releasing is Set-Mailbox user@contoso.com -LitigationHoldEnabled $false, and only on written instruction from whoever asked for the hold. After release, items in Recoverable Items are purged on the normal 14-day (configurable to 30) schedule, and a mailbox that was inactive is permanently deleted after its retention winds down. If any other hold (retention policy, eDiscovery) still applies, the content stays regardless — Get-Mailbox | fl InPlaceHolds lists them.