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Quick Answer

New Outlook for Windows does not yet support COM add-ins, PST file import, offline shared mailboxes, or some advanced rules. If you need these features, switch back to Classic Outlook by toggling off Try the new Outlook in the top-right corner.

Understanding the Missing Features in "New" Outlook ​

Estimated Time to Fix: 3 minutes

Applies to: New Outlook for Windows, Classic Outlook
Article Type: Informational
Last Updated: 2026-07-20

Summary ​

Microsoft is slowly transitioning users from "Classic" Outlook to the "New" Outlook for Windows. However, New Outlook is fundamentally different under the hood (it is built on web technology) and is missing several legacy features. This article outlines the major differences to help you decide if you should switch.

Prerequisites ​

  • None required.

Instructions ​

1. Features Completely Missing in New Outlook ​

As of late 2026, if your daily workflow relies heavily on the following features, you should not switch to New Outlook yet.

  • PST File Support: You cannot open or import local .pst data files. All mail must be hosted in the cloud.
  • COM Add-ins: Traditional plugins (like custom CRM integrations, advanced PDF creators, or legacy macro suites) will not work. Only modern web-based add-ins are supported.
  • Offline Access: While limited offline support is being tested, New Outlook requires a constant internet connection for most daily tasks.
  • Advanced Folder Views: You cannot heavily customize your inbox view (e.g., conditional formatting based on complex rules, or grouping by custom metadata).

2. Features That Behave Differently ​

Some features exist but require you to change how you work:

  • Shared Mailboxes: They do not auto-map seamlessly. You often have to add them manually, and they appear lower in the folder pane rather than as fully separate top-level accounts.
  • Signatures: Signatures sync to the cloud rather than saving to your local computer. You must recreate them if you relied on complex local HTML signatures.
  • Rule Limitations: Client-only rules (rules that require Outlook to be running to execute) are no longer supported. All rules must be server-side.

3. How to Switch Back to Classic Outlook ​

If you tried New Outlook and found it lacking a critical feature, reverting is simple.

  1. Open New Outlook.
  2. Look at the very top right corner of the window.
  3. You will see a toggle switch labeled New Outlook.
  4. Click the switch to turn it Off.
  5. The application will close and automatically reopen in Classic Outlook. Your emails and settings will be right where you left them.

Troubleshooting ​

TIP

Microsoft frequently updates New Outlook. If a feature you need is missing today, it may be added in the coming months. Keep an eye on IT announcements regarding Outlook migrations.

Symptom / ErrorPotential CauseSolution
The "New Outlook" toggle is missing entirelyIT PolicyYour company may have forced the migration to New Outlook via an IT policy. Contact the Help Desk to request a temporary exception.
New Outlook crashes when adding an accountUnsupported account typeNew Outlook struggles with legacy POP3 or IMAP accounts. Use an Exchange or Microsoft 365 account.