When using Copilot in Outlook, you may find that it cannot read or summarize emails stored in public folders. This limitation occurs because Copilot relies on Microsoft Graph, which does not index public folder content by default. Understanding this access gap helps you avoid confusion and plan alternative workflows. This article explains why public folders are excluded, how Copilot handles them, and what you can do to work around the limitation.
Key Takeaways: Copilot and Public Folders in Outlook
- Microsoft Graph indexing scope: Copilot can only access data indexed in Microsoft Graph, which excludes on-premises Exchange public folders.
- No summarization or drafting: Copilot cannot summarize, draft replies, or extract insights from public folder emails because the content is not searchable via Graph.
- Migration to Microsoft 365 Groups: Moving public folder content to Exchange Online mailboxes or Microsoft 365 Groups restores Copilot compatibility.
Why Copilot Cannot Access Public Folders
Copilot in Outlook works by querying the Microsoft Graph API for email, calendar, and contact data. Public folders in Exchange Online or on-premises Exchange are stored in a separate database hierarchy that Microsoft Graph does not index. This is by design: public folders are legacy shared mailboxes that do not expose their content through the same REST endpoints as user mailboxes.
Even if your organization uses Exchange Online, public folders created before migration or those synced from on-premises remain outside the Graph indexing scope. Copilot sees only the folder structure but cannot read the individual messages. This means any feature that depends on message content, such as summarization, suggested replies, or contextual insights, will fail or return empty results.
Public Folders vs Shared Mailboxes
Shared mailboxes are indexed by Microsoft Graph when they are licensed with an Exchange Online Plan 2 or higher. Copilot can read and process emails in shared mailboxes if the user has delegate access. Public folders, however, do not have a mailbox-level license and rely on a different permission model. This structural difference is the root cause of the access limitation.
What Copilot Can and Cannot Do With Public Folders
Understanding the exact boundaries helps you set realistic expectations when working with Copilot in Outlook.
- Cannot summarize public folder emails
When you select an email in a public folder, the Copilot pane shows no summarization option. The “Summarize” button remains grayed out or produces an error stating the content is unavailable. - Cannot draft replies from public folder context
Copilot uses the current email thread to generate drafts. Because it cannot read the thread in a public folder, the “Draft with Copilot” feature is disabled. - Cannot search public folder content via Copilot
The Copilot chat panel in Outlook searches only indexed mailboxes. Queries about public folder content return no results, even if the user has full access permissions. - Can display public folder names in folder list
Copilot can see the folder hierarchy and display folder names because that metadata is available through Graph. The limitation applies only to the message bodies and attachments inside the folders.
Workarounds for Using Copilot With Public Folder Content
If your team relies on public folders and wants to use Copilot, consider these alternative approaches.
Move Content to Shared Mailboxes
- Create a shared mailbox in Exchange admin center
Go to Exchange admin center > Recipients > Shared mailboxes. Click Add a shared mailbox and assign a license with Exchange Online Plan 2. - Export public folder emails to PST
In Outlook, open the public folder, select the emails, and choose File > Open & Export > Import/Export. Select Export to a file, then Outlook Data File PST. - Import PST into the shared mailbox
Open the shared mailbox in Outlook. Use File > Open & Export > Import/Export, select Import from another program or file, and choose the PST file. Map the source folder to the shared mailbox Inbox. - Grant delegate access
In Exchange admin center, select the shared mailbox, click Mailbox delegation, and add users with Full Access and Send As permissions.
Migrate Public Folders to Microsoft 365 Groups
- Assess public folder structure
List all public folders and identify which ones are actively used. Microsoft 365 Groups work best for collaboration with a dedicated mailbox and site. - Create a Microsoft 365 Group
In Outlook, go to Home > New Group. Enter a name, description, and add members. The group automatically creates a shared mailbox and calendar. - Copy emails from public folder to group mailbox
Open both the public folder and the group mailbox side by side. Select emails in the public folder and drag them into the group Inbox. Or use the Move to option from the ribbon. - Verify Copilot access
Open an email in the group mailbox. The Copilot pane should show the Summarize option and enable Draft with Copilot.
Use Search-Mailbox PowerShell for Bulk Moves
For large public folders with hundreds of emails, use the Exchange Management Shell to move content programmatically. The Search-Mailbox cmdlet with the -TargetMailbox and -TargetFolder parameters can copy messages to a shared mailbox or group mailbox while preserving metadata.
If Copilot Still Has Issues After Moving Content
Copilot Does Not Index Newly Moved Emails Immediately
After moving emails to a shared mailbox or group, Microsoft Graph requires time to index the new content. This process can take 15 minutes to a few hours depending on mailbox size. Wait at least one hour before testing Copilot features. If indexing fails, check the mailbox licensing in Exchange admin center.
Copilot Shows “Content Not Available” Error
This error appears when the mailbox is not licensed for Copilot. Verify that the shared mailbox or group mailbox has an Exchange Online Plan 2 license and that the user has a Copilot for Microsoft 365 license assigned. Without both licenses, Copilot cannot access any mailbox content, including moved emails.
Public Folder Permissions Block Copilot Even After Migration
If you copy emails manually without changing permissions, the new mailbox inherits permissions from the target mailbox, not the source public folder. Ensure that all users who need Copilot access have at least Contributor permissions on the target mailbox. Use Exchange admin center > Recipients > Shared mailboxes > Mailbox delegation to set Full Access permissions.
| Item | Public Folders | Shared Mailboxes |
|---|---|---|
| Microsoft Graph indexing | Not indexed | Indexed with Exchange Online Plan 2 license |
| Copilot summarization | Not available | Available |
| Copilot draft replies | Not available | Available |
| Permission model | Folder-level permissions | Mailbox-level delegation |
| Migration effort | Baseline | Medium: export PST or use PowerShell |
Copilot in Outlook cannot access public folder emails because Microsoft Graph does not index public folder content. To use Copilot features such as summarization and drafting, move the content to a shared mailbox or Microsoft 365 Group that is licensed with Exchange Online Plan 2. After migration, allow indexing time and verify that the target mailbox has the correct permissions and licenses. For ongoing access, consider converting remaining public folders to shared mailboxes and retiring the public folder infrastructure.