Cant Open Outlook

Yes—Microsoft Outlook and other Microsoft 365 services experienced a widespread outage on November 12–13, 2026, so a new Outlook access failure today may be service-related rather than a problem with your PC.^1^

Check whether your organization is affected

1. Ask your Microsoft 365 administrator to open Microsoft 365 admin center → Health → Service health and review active incidents for Outlook or Exchange Online.
2. Check whether coworkers are experiencing the same issue.
   • Multiple users affected: wait for the service incident to be resolved.
   • Only your PC affected: continue with the local checks below.
3. During the outage, use Outlook on the web or new Outlook for Windows if either remains available. Microsoft documents these as workarounds for certain service-side Classic Outlook startup failures.[^2^](https://support.microsoft.com/support/known-issues/error-when-opening-classic-outlook-cannot-start-microsoft-outlook-cannot-open-the-outlook-window-the "Error when opening classic Outlook: "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed." | Microsoft Support")

If only Classic Outlook on your PC remains affected

Run Microsoft’s Classic Outlook startup troubleshooter on the affected PC. It requires Windows 10 or later:

1. Open Microsoft’s startup support page.
2. Select Try guided support.
3. When prompted that the site wants to open Get Help, select Open.
4. Complete the diagnostic prompts.^3^

If that does not resolve it, test without add-ins:

1. Press Windows key + R.
2. Enter:

      Outlook /safe
   

3. Select OK, accept the default profile, and sign in if prompted.
4. If Outlook opens, go to File → Options → Add-ins.
5. Beside Manage: COM Add-ins, select Go.
6. Record the enabled add-ins, then clear their checkboxes—do not select Remove.
7. Restart Outlook normally and re-enable the add-ins individually until the failure returns.^3^

If Outlook will not start even in safe mode, the same Microsoft procedure recommends creating and testing a new Outlook profile. Before removing an existing profile, back up any required data files because removing it deletes locally cached content.^3^

References

1. Microsoft platforms including Outlook suffer widespread outages
2. Error when opening classic Outlook: "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed." | Microsoft Support
3. I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support