Copilot in Outlook Litigation Hold Awareness: What It Reads and Skips

When you use Copilot in Outlook to summarize an email thread or draft a reply, you may wonder whether messages under a litigation hold are included in the response. Litigation holds preserve all mailbox content for legal or compliance purposes, and Copilot must respect these holds to avoid surfacing protected data. This article explains exactly which mailbox items Copilot reads and which items it skips when a litigation hold is active. You will learn the technical boundaries of Copilot’s data access, how to verify what Copilot can see, and the settings that control this behavior.

What Copilot Reads and Skips in a Litigation Hold Mailbox

Microsoft 365 litigation hold preserves all mailbox content in place. This means the items remain in the same folders but cannot be permanently deleted by the user. Copilot in Outlook accesses the same mailbox data that Outlook displays. However, Copilot applies additional filters to respect legal holds.

Copilot reads items that are visible in the user’s default mailbox folders: Inbox, Sent Items, Drafts, Deleted Items, and user-created folders. If a mailbox is under litigation hold, Copilot can still read these items because the hold does not hide them. The hold only prevents deletion. Copilot skips items that are in the Recoverable Items folder or any folder that is not visible to the user in the Outlook folder list. This includes the Purges, Versions, and DiscoveryHolds folders within the Recoverable Items structure.

How Litigation Hold Affects Copilot Summaries

When you ask Copilot to summarize an email conversation that includes items under litigation hold, Copilot processes only the items it can access. If the conversation contains messages that are in the Recoverable Items folder — for example, a message that was soft-deleted and still preserved under hold — Copilot skips those messages entirely. The summary will include a note that some content was not available due to compliance policies.

When Copilot Skips an Entire Mailbox

Copilot does not skip an entire mailbox simply because a litigation hold is active. The hold alone does not block Copilot access. Copilot skips an entire mailbox only if the mailbox is placed on a specific compliance hold that explicitly restricts Copilot processing. This is controlled by the Copilot data access policy in the Microsoft 365 admin center. If that policy is configured to block Copilot for held mailboxes, Copilot shows a message that the mailbox is not available for AI processing.

Steps to Verify What Copilot Reads in a Litigation Hold Mailbox

You can check which items Copilot can access by running a simple test in Outlook. Follow these steps.

1. Open Outlook and select a mailbox under litigation hold
   Verify the litigation hold status in the Microsoft 365 admin center under Purview > eDiscovery > Litigation hold. Confirm the hold is active for the mailbox you want to test.
2. Open the Copilot pane in Outlook
   Click the Copilot icon in the Outlook ribbon or press Alt+I to open the Copilot pane. The pane appears on the right side of the Outlook window.
3. Select an email thread that contains soft-deleted items
   Choose a conversation where at least one message was moved to the Deleted Items folder and then permanently deleted. The soft-deleted item is now in the Recoverable Items folder and is under litigation hold.
4. Ask Copilot to summarize the thread
   Type “Summarize this email thread” in the Copilot prompt box and press Enter. Copilot processes the visible messages only.
5. Check the summary for the exclusion note
   Read the summary output. If Copilot skipped any messages due to litigation hold, the summary includes a sentence such as “Some messages in this thread were not available due to compliance policies.”

If Copilot Still Reads Held Items or Shows Errors

Even with litigation hold active, you may encounter situations where Copilot behaves unexpectedly. Below are the most common scenarios and their fixes.

Copilot Summarizes a Thread That Includes a Litigation Hold Message

This happens when the held message is still in a visible folder such as Inbox or Sent Items. Litigation hold does not move messages to a hidden folder. The hold only prevents deletion. To confirm the item is truly under hold, check the Hold status column in Outlook. If the message shows a hold icon, Copilot can still read it because it is in a visible folder. To restrict Copilot from reading such items, apply a compliance hold that blocks Copilot data access.

Copilot Shows “This mailbox is not available for Copilot”

This error appears when the mailbox is placed under a compliance hold that explicitly disables Copilot processing. The fix requires an admin to modify the Copilot data access policy. Go to Microsoft 365 admin center > Settings > Copilot > Data sources. Under Mailbox exclusions, remove the mailbox from the exclusion list. This change takes effect within 15 minutes.

Copilot Returns an Empty Summary or No Output

An empty summary can occur when all messages in the selected thread are in the Recoverable Items folder. This is common in mailboxes that were recently placed on litigation hold and had many soft-deleted items. To verify, open the thread in Outlook and check the folder location of each message. If all messages are in the Recoverable Items folder, Copilot cannot process them because that folder is not indexed. The only workaround is to restore the messages to a visible folder using the eDiscovery export tool.

Copilot Standard Access vs Copilot Under Litigation Hold: Key Differences

Item	Copilot Standard Access	Copilot Under Litigation Hold
Visible folders indexed	Inbox, Sent Items, Drafts, Deleted Items, user folders	Same as standard access
Recoverable Items folder	Not indexed	Not indexed
Soft-deleted messages	Not accessible	Not accessible
Copilot exclusion note	Not present	Present when held items are skipped
Admin override via Copilot policy	Available	Available

Now you know exactly what Copilot reads and skips when a litigation hold is active. To test this behavior in your own tenant, run the verification steps above with a test mailbox. For tighter control, adjust the Copilot data access policy in the Microsoft 365 admin center to exclude specific held mailboxes from processing. This approach gives you both compliance and transparency in how Copilot handles preserved content.