MY OUTLOOK CLASSIC WONT OPEN

Kathleen Allan 0 Reputation points
2026-11-09T09:32:25.8266667+00:00

WHY WONT MY OUT LOOK OPEN IY KEEP SAYING ITS RUN INTO A Error

Outlook | Windows | Classic Outlook for Windows | For home
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  1. Emma1-N 14,920 Reputation points Microsoft External Staff Moderator
    2026-11-10T03:53:59.9966667+00:00

    Welcome Kathleen Allan,

    Thanks for reaching out to Microsoft Q&A Forum. I understand that classic Outlook for Windows will not open and keeps showing a message that it has run into an error.

    To help narrow this down, could you please share:

    • The exact error message, or a screenshot of it (please hide any email addresses).
    • What type of email account you use in Outlook, for example Outlook.com, Gmail, Yahoo or another provider.

    Please make sure you already tried the Q&A Assist steps. In addition, please try the following:

    1, Make sure Outlook is not already running in the background

    • Press Ctrl + Shift + Esc to open Task Manager.
    • Under Processes, find any Microsoft Outlook entries, right-click each one and select End task.
    • Right-click the Outlook shortcut and select Properties, then open the Compatibility tab. Make sure Run this program in compatibility mode for is unchecked, then select OK.
    • Start Outlook again.

    2, Update Microsoft 365 or Office from another Office app

    • Open Word and create a blank document.
    • Go to File, then Account.
    • Under Product Information, select Update Options, then Update Now.
    • Restart the computer after the update finishes.

    3, Repair the Outlook data file (.pst) with the Inbox Repair tool

    • Close Outlook. Back up your .pst file before running the tool.
    • Open File Explorer and go to C:\Program Files\Microsoft Office\root\Office16, or C:\Program Files (x86)\Microsoft Office\root\Office16.
    • Open SCANPST.EXE, select Browse, choose your .pst file, then select Start.
    • If errors are found, select Repair. You may need to run the tool more than once.

    4, Rebuild the offline data file (.ost), if your account is Outlook.com or Microsoft 365

    • Close Outlook.
    • Press Windows key + R, type %localappdata%\Microsoft\Outlook and select OK.
    • Rename the .ost file for your account, for example by adding .old to the end of the name.
    • Start Outlook. It will create a new file and download your mail again from the server.

    Looking forward to your update.

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  2. AI answer

    2026-11-09T09:34:27.9466667+00:00

    Start classic Outlook in Safe Mode first; if it stays open there, disable its add-ins because one of them is likely causing the closing error.

    1. Test Outlook in Safe Mode

    1. Press Windows key + R.
    2. Type: 
         Outlook.exe /safe
    3. Select OK, accept the default profile, and enter your password if requested.

    If Outlook remains open:

    1. Select File → Options → Add-ins.
    2. At the bottom, choose COM Add-ins → Go.
    3. Take a picture of the enabled add-ins, then clear their check boxes. Do not select Remove.
    4. Restart Outlook normally.
    5. If it works, re-enable one add-in at a time, restarting Outlook after each one. Leave the add-in that causes the error disabled. ^1^

    2. If Safe Mode also closes

    Reset Outlook’s navigation pane:

    1. Close Outlook.
    2. Press Windows key + R.
    3. Enter: 
         Outlook.exe /resetnavpane
    4. Select OK.

    This removes navigation-pane customizations but does not delete email. ^1^

    3. Check the recent Windows-update condition

    If this problem began immediately after a Windows update and your Outlook account uses POP or a .pst file, install the newest Windows updates first:

    1. Open Start → Settings → Windows Update.
    2. Select Check for updates.
    3. Install everything offered and restart the computer.

    A known issue affected some POP/PST configurations, and its correction was included in newer Windows builds. ^2^

    If Windows is fully updated and Outlook stopped working immediately after one identifiable update, temporarily uninstalling that update can be used as a test:

    Settings → Windows Update → Update history → Uninstall updates

    Removing an update can reduce security. If this is a work or school computer, contact the IT administrator instead.

    4. Repair Microsoft 365 or Office

    The correct path depends on the Windows version:

    • Windows 11: Right-click Start → Installed apps → Microsoft 365 or Office → three dots → Modify.
    • Windows 10: Right-click Start → Apps and Features → Microsoft 365 or Office → Modify.

    Choose Quick Repair first. If Outlook still fails, repeat the process and choose Online Repair; this is more thorough and may require an internet connection. Restart afterward. ^3^

    5. Create a fresh Outlook profile

    If repair does not help:

    1. Press Windows key + R.
    2. Enter: 
         Outlook.exe /profiles
    3. Select Options → New.
    4. Give the profile a name and add your email account.
    5. Start Outlook and select the new profile.

    If Outlook opens with the new profile, the original profile was damaged. Do not remove the old profile until any locally stored data has been backed up. ^4^

    References

    1. I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support
    2. Outlook (Classic) error - Microsoft Q&A
    3. Repair an Office application
    4. Create a profile in classic Outlook for Windows
    AI-generated content may be incorrect. Read our transparency notes for more information.

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