Urgent help for, Outlook is not working

Question

Hi, since Monday, Outlook is not working for [Moderator note: personal info removed] business.

Answer 1

Dear @N & S Team ,

Thank you for posting your question in the Microsoft Q&A forum.

Please understand that our forum is a public platform, and we will modify your question to cover your organization domain name in the description. Please notice to hide these personal or organization information next time you post error or some information to protect personal data.

Based on your description, your Outlook is not working since Monday. For better understanding, could you please provide more information as:
Is the issue occurring in Outlook desktop app, Outlook on the web, or both? New Outlook or Classic Outlook?

Does it appear any specific error message when the issue occurs?

Have you checked does the issue affect all users in your organization, or only specific accounts?

It would be helpful if you could share screenshot of the issue (please remove/hide private information in screenshot)

Please understand that the more information you provide, the more effectively I can support you.

Thank you for your cooperation.
Looking forward to your update.

Answer 2

Troubleshooting steps for Outlook not working depend on the exact symptom (not opening, freezing, or not sending/receiving). For a business scenario, start with the following checks on each affected machine:

1. Confirm Outlook is not just busy or waiting
   • Check the Outlook status bar for background tasks such as sending/receiving large attachments or auto-archive. If a process is running, wait a few minutes to see if Outlook recovers.
2. Start Outlook in Safe Mode (classic Outlook for Windows)
   • Close Outlook.
   • In Windows 10, select Start, type Outlook.exe /safe, and press Enter.
   • If Outlook opens in Safe Mode, close it and reopen normally to see if the issue is resolved.
3. Check for open dialog boxes
   • Press Alt+Tab to see if a hidden Outlook dialog (for example, a confirmation prompt) is blocking interaction. Close or respond to any such dialog and test Outlook again.
4. Install latest Windows and Office updates
   • Make sure Windows Update and Microsoft 365/Office updates are fully installed, including important, recommended, and optional updates. See Install Office updates.
5. Repair Office
   • Close all Microsoft 365 apps.
   • Open Control Panel → Programs and Features.
   • Right-click the Office/Microsoft 365 installation and choose Change → run a Quick Repair first; if the issue persists, run an Online Repair.
6. Repair Outlook data files (classic Outlook)
   • Close Outlook.
   • Run the Inbox Repair Tool (SCANSPST.EXE) as described in Repair Outlook Data Files (.pst and .ost) to scan and repair the data files.
7. If using POP accounts and Outlook is freezing after a recent Windows 11 update
   • There is a known issue where classic Outlook POP profiles hang and freeze after installing Windows 11 update KB5074109. The temporary fix is to uninstall the January 2026 update KB5074109 via Settings → Windows Update → Update history → Uninstall updates, then test Outlook again.
8. If using the new Outlook for Windows and it fails shortly after launch
   • Run olk.exe --clearLocalState to reset the new Outlook local state, then start the new Outlook again and re-enter account credentials when prompted.

If these steps do not restore Outlook for the business, use the classic Outlook troubleshooters described in the context article “Issues sending and receiving email” and, if still unresolved, contact Microsoft support for tenant-level investigation.

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References:

• Outlook not responding, stuck at "Processing," stopped working, or freezes
• Outlook for Windows not responding, hangs, freezes, or stops working
• Classic Outlook not responding, stuck at "Processing," stopped working, or freezes
• Outlook not responding error or Outlook freezes when you open a file or send mail
• Issues sending and receiving email
• New Outlook has stopped working, Fails when starting after 30 to 60 seconds - Microsoft Q&A
• Outlook Freezing and Not Responding and Not saving changes when ending the task - Microsoft Q&A
• What to do when Outlook will not open on my PC? - Microsoft Q&A
• Detected a problem launching new Outlook - Microsoft Q&A
• Outlook keeps crashing - Microsoft Q&A