New Outlook Public Folders Partially Available: Best Workaround

If you use the new Outlook for Windows and work with shared mailboxes, you may have noticed that public folders are only partially available. Some folders appear empty, others fail to load, and certain hierarchy branches are missing entirely. This limitation exists because the new Outlook does not fully support the legacy public folder infrastructure used by on-premises Exchange Server or hybrid deployments. This article explains why public folders are incomplete in the new Outlook and provides the most reliable workaround to restore full access.

The root cause is that the new Outlook uses a sync engine designed primarily for Microsoft 365 cloud mailboxes and does not connect to the Exchange Server public folder database the same way classic Outlook does. While Microsoft has added basic public folder browsing in the new Outlook, many features such as folder permissions, custom forms, and nested hierarchies are not supported. The workaround described below lets you access all public folder content using the classic Outlook client while keeping the new Outlook for your daily email tasks.

Why Public Folders Are Incomplete in the New Outlook

The new Outlook for Windows is built on a different codebase than classic Outlook. It uses the Microsoft Sync Framework and relies on REST APIs to connect to mailboxes and shared folders. Public folders, however, are stored in a separate database on Exchange Server (on-premises or hybrid) and are accessed via the MAPI protocol and the Exchange Web Services (EWS) public folder endpoint. The new Outlook does not include a MAPI client stack, so it cannot enumerate the full public folder hierarchy or retrieve items from all folder types.

In practice, this means the new Outlook may show only the top-level public folders or a subset of folders that are replicated to Microsoft 365. Folders with custom permissions, mail-enabled public folders, and folders deeper than two levels in the hierarchy often appear empty or fail to expand. Microsoft has acknowledged this limitation and is working on improvements, but as of now, full public folder support is not available in the new Outlook.

What Does “Partially Available” Mean Exactly?

When you navigate to public folders in the new Outlook, you may see the folder list but receive an error when you try to open a folder. Common error messages include “Cannot expand the folder” or “The set of folders cannot be opened.” In other cases, the folder appears but contains no items, even though the same folder has hundreds of messages in classic Outlook. This partial availability affects all public folder types: mail, calendar, contacts, and tasks.

Best Workaround: Use Classic Outlook for Public Folders

The most reliable workaround is to run classic Outlook alongside the new Outlook. You do not need to uninstall the new Outlook or reconfigure your mailbox. You simply use the toggle to switch between clients based on the task at hand. Use the new Outlook for email, calendar, and contacts. Use classic Outlook for all public folder operations.

Step 1: Switch to Classic Outlook Using the Toggle

1. Locate the toggle
   In the new Outlook, look at the top-right corner of the window. You will see a toggle switch labeled “New Outlook.” If the toggle is blue, you are using the new Outlook.
2. Turn off the toggle
   Click the toggle to turn it off. A dialog box appears asking if you want to switch to classic Outlook. Click Yes. Outlook closes and reopens in classic mode.
3. Verify classic Outlook is running
   Check the title bar. It should say “Outlook” without “New” in the title. The ribbon at the top shows the classic File, Home, Send/Receive, and Folder tabs.

Step 2: Access Public Folders in Classic Outlook

1. Open the Folder Pane
   In classic Outlook, go to View > Folder Pane > Normal if the folder pane is not visible.
2. Navigate to Public Folders
   Scroll to the bottom of the folder pane. Expand Public Folders > All Public Folders. You will see the full hierarchy of public folders as configured on your Exchange Server.
3. Open a public folder
   Double-click any folder to view its contents. All items, including mail, calendar events, and contacts, appear as expected.

Step 3: Add Frequently Used Public Folders to Favorites

1. Right-click the public folder
   In classic Outlook, right-click the public folder you access most often.
2. Select “Add to Favorites”
   From the context menu, choose Add to Favorites. The folder appears under the Favorites section in the folder pane.
3. Switch back to the new Outlook
   Click the New Outlook toggle in the top-right corner and confirm the switch. The new Outlook opens again. Your public folders are now one click away in classic Outlook whenever you need them.

If the Toggle Is Missing or Greyed Out

Some organizations disable the toggle via Group Policy or registry settings. If the toggle is missing or greyed out, you can still run both versions of Outlook on the same computer.

Run Classic Outlook Without Using the Toggle

1. Close the new Outlook completely
   Right-click the Outlook icon in the system tray and select Exit.
2. Open classic Outlook from the Start menu
   Press the Windows key, type Outlook, and select Outlook (classic) from the search results. If you see only one Outlook entry, it is likely the classic version.
3. Pin classic Outlook to the taskbar
   Right-click the Outlook icon on the taskbar while classic Outlook is running and select Pin to taskbar. This gives you quick access to classic Outlook without using the toggle.

Alternative Workaround: Use Outlook on the Web

If you cannot use classic Outlook, Outlook on the Web (OWA) provides better public folder support than the new desktop client. OWA uses the same EWS endpoints that classic Outlook uses for public folders.

1. Open OWA in your browser
   Go to outlook.office.com or your organization’s OWA URL.
2. Navigate to public folders
   In the left folder pane, scroll down and expand Public Folders. The full hierarchy loads.
3. Use OWA only for public folders
   Keep the new Outlook open for everything else. OWA runs in a browser tab and does not interfere with the desktop client.

New Outlook vs Classic Outlook: Public Folder Feature Comparison

Item	New Outlook	Classic Outlook
Public folder hierarchy	Partial (top-level only)	Full hierarchy
Folder permissions	Not supported	Supported
Custom forms	Not supported	Supported
Mail-enabled public folders	May show as empty	Fully functional
Calendar public folders	Not supported	Supported
Contacts and tasks public folders	Not supported	Supported
Nested folders (3+ levels)	Cannot expand	Fully expandable
Search within public folders	Limited	Full search

Common Issues When Using the Workaround

Classic Outlook Prompts for Credentials Every Time I Switch

This happens when classic Outlook uses a different authentication method than the new Outlook. Open classic Outlook, go to File > Account Settings > Account Settings, select your account, and click Change. Under Offline Settings, select Use Cached Exchange Mode and set the slider to All. This caches your credentials and reduces repeated prompts.

Public Folders Are Still Missing in Classic Outlook

If classic Outlook does not show public folders at all, your mailbox may be configured for Microsoft 365 only. Check with your Exchange administrator to confirm that your mailbox has permission to access the public folder database. In some hybrid deployments, the public folder mailbox must be added manually in classic Outlook: File > Account Settings > Account Settings > Change > More Settings > Advanced > Add, then enter the public folder mailbox name.

The New Outlook Keeps Reverting to Classic Mode

This occurs when an organization policy forces the use of classic Outlook. If you see a message that says “Your organization requires classic Outlook,” the toggle is effectively disabled. Use the alternative workaround: run classic Outlook from the Start menu and pin it to the taskbar. Do not attempt to bypass the policy.

Conclusion

You can now access public folders in the new Outlook by using classic Outlook as a companion client. Keep the new Outlook running for your daily email and calendar tasks, and switch to classic Outlook or Outlook on the Web whenever you need to browse, read, or manage public folder content. For quick access, add your most-used public folders to Favorites in classic Outlook before switching back. As a next step, ask your Exchange administrator whether your organization plans to migrate public folders to Microsoft 365, which would resolve this limitation permanently. If you frequently work with custom forms or deeply nested public folders, consider keeping classic Outlook as your primary client until the new Outlook adds full support.