Outlook always asks for repairing a damaged OST file

Christian Bisti 20 Reputation points

Client Outlook 365 - Microsoft 365 mail account

A few weeks ago Outlook started finding the corrupted OST file and asking for its repair. Being a very large file, I preferred to set Outlook to online mode (without cache file) and then delete the damaged OST file, with the intention of having it recreated later.

I then deleted all cache files in C:\Users[USER]\AppData\Local\Microsoft\Outlook and reset Outlook to "normal" mode, but on first boot it asked me again to repair the OST file (which was non-existent at this point).

I went into the registry (HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\XX.0\Outlook\PST) and modified the entries "LastCorruptStore" (deleted the value referring to the OST file) and "PromptRepair" (set to 0). Restarted Outlook, but the message still appears.

I then tried to remove those two registry keys altogether, but that didn't help.

So I completely deleted the profile and created a new one...but the error still pops up!

Where else can I look?

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Office Management
Office Management
Office: A suite of Microsoft productivity software that supports common business tasks, including word processing, email, presentations, and data management and analysis.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Faery Fu-MSFT 13,206 Reputation points Microsoft Vendor

    Thanks for your feedback above which shared more information and glad to know that your issue is resolved now! Since our forum has the policy that the question author cannot accept their own answer. They can only accept answers by others, and according to the scenario introduced here: Answering your own questions on Microsoft Q&A

    I would make a brief summary of this post so that other forum members could easily find useful information here:

    [Activating lagged copies - Summary]

    Issue Symptom:

    Outlook with cached mode always asks for repairing a damaged OST file.


    Create a new profile with a different name and manually add your account.

    Besides, if you want to delete the profile name “Outlook” , follow the steps below.

    Hold the Windows key and press R, type regedit and hit OK.

    Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Profiles

    Screenshot 2023-09-08 134238

    You could "Accept Answer" for this summary to close this thread, and your action would be helpful to other users who encounter the same issue and read this thread. Thanks for your understanding!

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3 additional answers

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  1. Faery Fu-MSFT 13,206 Reputation points Microsoft Vendor

    Hi @Christian Bisti ,

    In order to verify, does this problem also exist in cached mode? And how did you create a new profile?

    I understand that you have tried many possible solutions, but none of them worked. Here are some suggestions that might help you fix the corrupted OST file in Outlook 365:

    • It is recommended you follow these steps to create a new profile and set it as default. Go to Control Panel > Mail > Show Profiles > Add, type a name for the new profile and select the option to use the new profile as the default profile.
    • Repair your Office installation. Sometimes, repairing Office can fix issues with Outlook and other applications. Go to Control Panel > Programs and Features, right-click your Office product and select Change, select Online Repair or Repair.
    • Update your Office to the latest version. Updating Office can help resolve bugs and improve performance. Open any Office application, click File > Account (or Office Account if you use Outlook). Under Product Information, click Update Options > Update Now.

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

  2. Christian Bisti 20 Reputation points

    I've tried to completely reinstall Office... same result

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  3. Christian Bisti 20 Reputation points


    After the reinstallation, I've tried to create a new Outlook profile WITH A DIFFERENT NAME, and it worked. A new OST file was created and now all is working well, while the classic profile name "Outlook" continued to return error

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