The toggle to switch between Classic Outlook and New Outlook is a feature that lets users move between two versions of the Outlook desktop app. This toggle appeared after Microsoft released the New Outlook preview for Windows. Many users find the toggle confusing because it changes the interface, features, and account configuration. This article explains what the toggle does, how the underlying program changes, and what users should know before switching.
Key Takeaways: What the Classic vs New Outlook Toggle Actually Does
- Toggle location in Classic Outlook: Top-right corner next to the settings gear icon. In New Outlook, the toggle is under Help > Switch to Classic Outlook.
- Profile and account separation: New Outlook uses a single Microsoft 365 profile. Classic Outlook loads your existing mail profiles (PST, Exchange, IMAP) independently.
- Feature loss when switching to New Outlook: No offline access, no COM add-ins, no custom forms, no shared mailbox auto-mapping via Exchange.
What the Classic Outlook vs New Outlook Toggle Changes
The toggle is not a simple visual switch. It launches a completely separate application engine. Classic Outlook is a full Win32 desktop application built on MAPI and the Outlook Object Model. New Outlook is a web-based shell that renders the Outlook Web App (OWA) interface inside a native container. When you flip the toggle, Windows stops the Classic Outlook process (OUTLOOK.EXE) and starts the New Outlook process (HxOutlook.exe).
The toggle exists because Microsoft is migrating Outlook to a unified codebase that matches the web and mobile versions. The New Outlook preview is the first step in that direction. The toggle gives users a way to test the new interface without permanently losing access to Classic Outlook features.
How the Toggle Affects Your Mail Profile
Classic Outlook uses mail profiles stored in the Windows registry and in %APPDATA%\Microsoft\Outlook. Each profile can contain multiple accounts, PST files, and cached data. New Outlook does not use these profiles. When you switch to New Outlook, the application reads your primary Microsoft 365 or Outlook.com account from Windows Credential Manager. Any IMAP or POP3 accounts configured in Classic Outlook do not appear in New Outlook unless you add them manually.
The toggle does not delete your Classic Outlook profile. Your PST files, rules, signatures, and account settings remain intact. When you switch back to Classic Outlook, everything returns exactly as you left it.
Feature Comparison: What Each Version Supports
Classic Outlook supports offline access, COM add-ins, custom forms, VBA macros, shared mailbox auto-mapping, and full PST management. New Outlook supports none of these. New Outlook does support integrated Microsoft To Do, the new Calendar board view, and a unified search across mail and calendar. The toggle is a trade-off between legacy functionality and modern interface features.
How to Switch Between Classic and New Outlook
The toggle works differently depending on which version you are currently using. Follow the steps for your current version.
Switch from Classic Outlook to New Outlook
- Open Classic Outlook
Launch Outlook from the Start menu or taskbar. Make sure you are signed in with your Microsoft 365 or Outlook.com account. - Locate the toggle
Look in the top-right corner of the window. Next to the gear icon, you see a toggle switch labeled Try the new Outlook. - Click the toggle to the On position
A prompt appears explaining that New Outlook is a preview. Click Yes to confirm. Outlook closes and reopens in New Outlook mode. - Wait for account sync
New Outlook loads your primary account. If you have multiple accounts, click File > Add Account to add each one manually.
Switch from New Outlook to Classic Outlook
- Open New Outlook
Launch the New Outlook app from the Start menu or click the Outlook icon in the taskbar. - Open the Help menu
Click the Help tab in the ribbon. If the ribbon is hidden, click the three dots (…) in the top toolbar and select Help. - Select Switch to Classic Outlook
In the Help menu, click Switch to Classic Outlook. A confirmation dialog appears. - Confirm the switch
Click Switch in the dialog. New Outlook closes and Classic Outlook opens. All your Classic Outlook profiles and settings are restored.
Common Problems When Using the Toggle
Toggle Is Grayed Out or Missing
The toggle is grayed out when your IT administrator has disabled New Outlook via Group Policy or the Microsoft 365 admin center. If you are using a work or school account, contact your admin. If you are using a personal account, ensure you are running Outlook version 2202 or later. Go to File > Office Account > About Outlook to check your version.
Accounts Disappear After Switching
New Outlook does not import IMAP or POP3 accounts from Classic Outlook. After switching, only your Microsoft 365 or Outlook.com account appears. To add other accounts, click File > Add Account and enter the email address and password. New Outlook supports IMAP, POP3, and Exchange accounts, but it does not support PST files.
Add-ins and Macros Stop Working
New Outlook does not support COM add-ins or VBA macros. If you rely on a third-party add-in for CRM, email tracking, or PDF handling, that add-in will not load in New Outlook. Switch back to Classic Outlook to use those add-ins. Microsoft has not announced a timeline for add-in support in New Outlook.
Classic Outlook vs New Outlook: Feature Comparison
| Item | Classic Outlook | New Outlook |
|---|---|---|
| Application type | Win32 desktop (MAPI-based) | Web shell (OWA-based) |
| Offline access | Full offline with Cached Exchange Mode | Limited offline for mail only |
| COM add-ins | Supported | Not supported |
| VBA macros | Supported | Not supported |
| PST file support | Full import/export and archive | Not supported |
| Shared mailbox auto-mapping | Automatic via Exchange | Manual add only |
| Custom forms | Supported | Not supported |
| Integrated Microsoft To Do | Separate app | Built-in |
| Calendar board view | Not available | Available |
| Unified search | Separate mail and calendar search | Single search box for all items |
The toggle is a temporary bridge between two generations of Outlook. Classic Outlook remains the fully supported version for enterprise environments that require offline access, add-ins, and PST management. New Outlook is the future platform, but it currently lacks many features that power users depend on.
Before switching, review the feature comparison table above. If your daily workflow depends on COM add-ins, VBA macros, or PST archives, stay with Classic Outlook. If you want the modern interface and can work without offline access, try New Outlook by flipping the toggle. You can switch back at any time using the Help menu.
For users who need both, consider running Classic Outlook and New Outlook side by side. Classic Outlook remains installed even when the toggle is on. You can launch Classic Outlook directly from the Start menu while New Outlook is open. This gives you access to legacy features in Classic Outlook while testing New Outlook for daily tasks.