outlook not working

The restoration time can only be determined from your organization’s Microsoft 365 Service health incident; the public status currently shows Microsoft 365 service degradation but does not confirm an Outlook or Hanoi-specific outage.^1^

Check whether Microsoft is fixing an outage

Ask your Microsoft 365 administrator to:

1. Sign in to the Microsoft 365 admin center.
2. Go to Health → Service health.
3. Check Exchange Online for an active incident or advisory.
4. Open the incident to see User impact, Status, Last updated, and Microsoft’s progress updates.

Service health is tenant-specific and is the authoritative place to determine whether your organization is affected and track restoration. Service Support and Helpdesk administrators can also view it.^2^

Meanwhile, use Outlook on the web. If the mailbox works there, you can continue working while troubleshooting Classic Outlook.

If no Exchange Online incident is listed

A frozen or non-opening Classic Outlook is then more likely to require local startup troubleshooting:

1. End the stuck process
   • Press Ctrl+Shift+Esc.
   • In Task Manager, select Microsoft Outlook → End task.
   • Reopen Outlook.
2. Run Microsoft’s startup troubleshooter
   • Open the Windows Get Help app.
   • Run the Classic Outlook startup troubleshooter and follow its prompts.
   • This requires Windows 10 or later and must run on the affected PC.^3^
3. Test Outlook without add-ins
   • Press Windows+R.
   • Enter:

          outlook.exe /safe
     

   • If Outlook opens, select File → Options → Add-ins.
   • Beside Manage: COM Add-ins, select Go.
   • Clear the add-in checkboxes—do not remove them—then restart Outlook normally.
   • Re-enable add-ins individually to identify the one causing the freeze.^4^
4. If Safe Mode also fails
   • Open Control Panel → User Accounts → Mail → Show Profiles.
   • Select Add, configure the Microsoft 365 work account, and start Outlook using the new profile.
   • If that does not help, go to Windows Settings → Apps → Installed apps → Microsoft 365 → Modify, run Quick Repair, and then Online Repair if needed.^4^

Do not uninstall a Windows security update based only on this symptom. The documented January 2026 hanging issue specifically concerned profiles with POP accounts and PST files; the stated account is a Microsoft 365 work or school account, so that condition has not been established.^5^

References

1. Microsoft service health status
2. How to check Microsoft 365 service health
3. I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support
4. [Classic Outlook](https://support.microsoft.com/outlook/getstarted/outlook-for-windows-not-responding-hangs-freezes-or-stops-working)
5. Fixes or workarounds for recent issues in classic Outlook for Windows