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Understanding the Missing Features in "New" Outlook

Applies toNew Outlook for WindowsClassic Outlook
3 min read Verified 3 Aug 2026

By , 10+ years in IT support and helpdesk How these guides are checked

Quick Answer

New Outlook for Windows still does not support COM add-ins, full offline access, or client-only rules. PST import and export both work now, but opening a PST to browse it needs Classic Outlook installed alongside. To go back, turn off the New Outlook toggle in the top-right corner.

Checked against Microsoft Learn - new Outlook for Windows, Microsoft Learn - end of support and retirement and between 5 Aug 2026 and 12 Sep 2026. Nothing published in that period has been linked to this guide.

Corrected 3 Aug 2026. This said new Outlook cannot handle PST files. Export shipped in mid-2025 and import during 2026, so the migration advice that followed from it was out of date. Opening a PST still needs Classic Outlook installed at a matching architecture. Every correction to this guide →
Estimated Time to Fix: 3 minutes

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.

Before You Start ​

  • None required.

Instructions ​

1. Features Completely Missing in New Outlook ​

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

  • 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:

  • PST Files: These work now, with one catch. Exporting your mailbox or chosen folders to a .pst has been supported since mid-2025, including scheduled repeat exports, and importing mail, calendars, and contacts from a .pst arrived during 2026. Opening a .pst to browse it still requires Classic Outlook to be installed on the same computer, and both must be the same architecture — 32-bit with 32-bit, or 64-bit with 64-bit. Microsoft has said it plans to drop that requirement during 2026. PST folders also do not sit in your folder list the way they do in Classic Outlook.
  • 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.

Last updated:

Frequently asked questions

Will my COM add-ins (like custom CRM tools) work in New Outlook?
No. New Outlook does not support legacy COM or VSTO add-ins. It only supports modern web-based add-ins downloaded from the Microsoft Store or deployed centrally by IT.
Can I export my email to a .pst file in New Outlook?
Yes. Exporting your mailbox or selected folders to a .pst file has been supported since mid-2025, and you can schedule repeat exports. Importing mail from a .pst arrived during 2026, followed by calendar and contact import.