Many business users are testing the new Outlook for Windows while relying on the classic Outlook for daily work. Switching between the two versions can cause missing accounts, lost signatures, or unexpected configuration changes if done incorrectly. This article explains the differences between the two versions, the exact steps to toggle between them, and how to protect your data during the transition. You will learn how to switch back and forth without losing settings or email access.
Key Takeaways: Switching Between New Outlook and Classic Outlook
- Toggle switch in new Outlook: Use the Try the new Outlook toggle in classic Outlook to enable the new version.
- Turn off new Outlook via File > Options > General: Access the same toggle from within the new Outlook to revert to classic.
- Back up your profile before switching: Export your AutoComplete list, signatures, and account settings to prevent data loss.
New Outlook vs Classic Outlook: What Changes When You Switch
The new Outlook for Windows is a web-based version of the app that uses Microsoft 365 cloud services. It does not support COM add-ins, local PST files, or certain legacy features such as shared mailbox automapping in the same way. Classic Outlook is the traditional Win32 desktop application that supports offline data files, custom forms, and most third-party add-ins. When you switch from classic to new, your accounts are copied to the cloud-based profile, but local settings such as signatures, rules, and autocorrect entries do not transfer automatically. When you switch back to classic, your original classic profile remains intact, but any changes you made in the new Outlook are not synced back to the classic profile.
What Is Preserved When You Switch
Your mailbox data remains on the Exchange server or IMAP server and is fully accessible in both versions. Calendar items, contacts, and email messages are not affected. Account credentials stored in Windows Credential Manager are reused, so you do not need to re-enter passwords each time.
What Is Not Transferred
Local settings that are stored in the classic Outlook profile are not migrated to the new Outlook. These include email signatures created in classic Outlook, custom stationery, Quick Steps, automatic reply templates, and the AutoComplete cache. Rules created in classic Outlook are stored on the Exchange server and do carry over, but rules created in the new Outlook may use a different format and might not appear in classic Outlook.
Steps to Switch From Classic Outlook to New Outlook
Before switching, close all instances of Outlook. If you have multiple profiles, ensure you are switching the correct one. Follow these steps to enable the new Outlook.
- Open classic Outlook
Launch Outlook from the Start menu or taskbar. Wait for the application to load fully and sync your mailbox. - Locate the Try the new Outlook toggle
In the top-right corner of the classic Outlook window, look for a switch labeled Try the new Outlook. If you do not see it, go to File > Options > General and check the box Enable the new Outlook. Click OK and restart Outlook. - Click the toggle to enable new Outlook
Click the toggle switch. A dialog box appears asking you to confirm. Click Try the new Outlook again. Outlook closes and reopens as the new Outlook. - Verify your accounts
In the new Outlook, click the gear icon in the top-right to open Settings. Under Accounts, confirm that all your email accounts are listed and syncing. Add any missing accounts manually using the Add Account option. - Set up signatures and rules again
Go to Settings > Mail > Signatures to recreate your email signatures. Go to Settings > Mail > Rules to recreate any rules that did not carry over.
Steps to Switch From New Outlook Back to Classic Outlook
If you prefer the classic version or need a feature that the new Outlook does not support, you can revert at any time.
- Open new Outlook
Launch the new Outlook from the Start menu or taskbar. - Go to File > Options > General
Click the File tab in the ribbon, then click Options. In the General category, locate the section labeled Try the new Outlook. - Turn off the toggle
Uncheck the box Enable the new Outlook. A confirmation dialog appears. Click OK. Outlook closes and reopens as classic Outlook. - Check your classic profile
In classic Outlook, verify that all your accounts appear in File > Account Settings. If an account is missing, add it manually. Your old signatures and rules should still be present because the classic profile was not deleted.
Common Issues When Switching Between Outlook Versions
Accounts Missing After Switching to New Outlook
The new Outlook only supports Exchange, Microsoft 365, IMAP, and POP accounts. If you use a third-party email provider that requires an app password or OAuth, you may need to re-add the account. Go to Settings > Accounts > Email accounts and click Add Account. Enter your email address and follow the prompts. If the account fails, check with your provider for IMAP settings.
Signatures and Quick Parts Do Not Appear After Switching
Signatures created in classic Outlook are stored in a local file on your computer. The new Outlook stores signatures in the cloud. You must manually recreate each signature in the new Outlook. To avoid losing your signatures, export them from classic Outlook before switching. In classic Outlook, go to File > Options > Mail > Signatures. Select each signature, copy the content, and paste it into a text file or save the signature file from the %appdata%\Microsoft\Signatures folder.
Outlook Crashes or Freezes After Switching
If the new Outlook crashes repeatedly, try disabling add-ins. In the new Outlook, add-ins are not supported, so crashes are usually caused by a corrupt profile or a conflicting Windows setting. Run the Outlook Inbox Repair Tool (scanpst.exe) on your classic Outlook data file if you suspect corruption. Alternatively, switch back to classic Outlook and run a repair from Control Panel > Programs > Microsoft 365 > Change > Quick Repair.
New Outlook vs Classic Outlook: Key Differences
| Item | New Outlook | Classic Outlook |
|---|---|---|
| Base technology | Web-based (Outlook Web Access wrapper) | Win32 desktop application |
| Offline access | Limited to cached Exchange mode | Full offline access with OST and PST files |
| COM add-ins support | Not supported | Full support |
| Local data files | No PST support | PST and OST support |
| Custom forms | Not supported | Full support |
| Signature storage | Cloud-based | Local file system |
| Quick Steps | Limited set | Full customization |
| Shared mailbox automapping | Manual add required | Automatic via AutoMapping |
How to Prepare Your Data Before Switching
Even though switching is safe, you should back up critical items to avoid rework. Export your AutoComplete list by running the command Outlook.exe /importprf in the Run dialog (Win+R) to create a profile backup. Copy your signatures folder from %appdata%\Microsoft\Signatures to a safe location. Export your rules by going to File > Manage Rules & Alerts > Options > Export Rules. Store these backups on OneDrive or a network drive so they are accessible from any device.
You can now switch between new Outlook and classic Outlook confidently because you know exactly what changes and what does not. After switching, always verify your accounts and recreate signatures as needed. For a permanent transition, consider testing the new Outlook for two weeks before committing fully.