How to Fix Error -"Unable to expand the folder, Client operation failed" in Outlook?

In Outlook, you can add shared folders, public folders, or secondary mailboxes and access all the mail folders and items in them. But sometimes, when you try to expand shared folders, public folders, or a mail folder from the secondary mailbox to access the mail items or view emails, you may encounter an error message, ‘Unable to expand the folder, Client operation failed’ or ‘Cannot expand the folder. Microsoft Outlook cannot access the specified folder.’ The error prevents you from expanding or opening the mail folders and accessing the messages.

In this article, you will learn the reasons that can prevent you from expanding Outlook folders and the solutions to resolve the issue.

Reasons for ‘Unable to expand the folder, Client operation failed’ Error

Following are some common reasons that may lead to the ‘Unable to expand the folder’ error and prevent Outlook users from accessing messages or mail items.

  • Permission issues
  • Oversized or large Outlook data file (OST)
  • Faulty or incompatible add-ins
  • Corrupt Outlook email profile
  • Damaged MS Office program files
  • Network issues

Solutions to Fix the Outlook Error “Unable to expand the folder, Client operation failed”

Follow the below solutions and workarounds to troubleshoot and fix the error in Microsoft Outlook 2021, 2019, 2016, 2013, and 2010.

Enable the Cached Exchange Mode

Cached Exchange Mode is highly recommended if you use Exchange or Microsoft 365 email accounts in Outlook. It provides a better user experience and Outlook performance. If the Cached Exchange Mode is disabled, you may encounter such errors while opening or expanding the mailboxes.

The steps to enable Cached Exchange Mode are as follows:

  • Open Microsoft Outlook and click File > Account Settings > Account Settings.
  • Choose Office 365/Microsoft 365 or Exchange email and click Change.
  • Click the Use Cached Exchange Mode option to download email to an Outlook data file and select the time using the slider.

Cache Account Settings

  • Click Next > Finish and restart Outlook.

Run Outlook in Safe Mode

You can open Outlook in Safe Mode to find out if any add-ins are causing the error. To run Outlook in Safe Mode and disable the add-ins, follow these steps:

  • Close Outlook and press Windows + R.
  • Type exe /safe and press the Enter key or click OK. The Outlook starts in Safe Mode.
  • Click File > Options > Add-Ins.
  • Click the Go button and uncheck all the add-ins to disable them.
  • Click OK to save changes and restart Outlook normally.

outlook add-in

  • Try to access or expand the mail folders. If the error is resolved, there could be faulty or incompatible add-in in the list which is causing the error.

To find which add-in is at fault, go to File > Options > Add-Ins > Go and enable one add-in. Restart Outlook to check if the error appears. Repeat the steps until the error pop-ups. Make sure to uninstall the add-in after which the error appeared to permanently fix the error.

Grant Full Access to the Mailbox

Sometimes, permission issues can also lead to such errors. It might happen that you don’t have the authorization to open or access mail items from a particular folder. You can resolve such issues by asking your administrator to allow you access to the particular folder where you are experiencing the ‘Unable to expand the folder, Client operation failed’ error message.

Use the Microsoft Support and Recovery Assistant (MSRA) Tool

MSRA is a proprietary tool from Microsoft to help resolve various issues with Microsoft Office applications. You can download and use the MSRA to fix this error in Outlook, configured with Microsoft 365 email account. The steps are as follows:

  • Download and install the MSRA on your system where you are experiencing the error.
  • After installation, open the MSRA tool and click ‘I agree.’

Microsoft support and recovery assistance

  • Choose Outlook and click Next.

microsoft support and recovery assistance

  • Choose Outlook Won’t Start or Other problems and click Next.
  • Select Yes and then click on Next.
  • Continue to follow the wizard. Use various options available in the MSRA to troubleshoot and fix the problem.

Reset Outlook Folders

Resetting the mail folders may help resolve issues or errors encountered while expanding the Outlook folders. The steps are as follows:

  • Close Outlook and press Windows + R.
  • Type Outlook.exe /resetfolders and click the OK button or press the Enter key to reset the Outlook folders.
  • Similarly, press Windows + R again and type Outlook.exe /resetfoldernames.

Outlook exe rest folder

  • Click OK or press the Enter key to reset the folder names to default.
  • Restart Outlook and try to expand or access the mail folders now.

Repair Microsoft Outlook

You may also try to repair MS Outlook to resolve the error. It’s quick and easy to repair MS Outlook. Follow these steps:

  • Open the Control Panel and click ‘Uninstall a program.’
  • Find and choose Microsoft Office from the list and click the Change button.

Control Panel and click ‘Uninstall a program.’

  • Choose the Repair or Quick Repair option, whichever is available (it varies based on the version you installed) and continue with the repair wizard to fix MS Outlook.
  • After the repair, restart the system.
  • Open MS Outlook and check if the error is solved.

Create a New Outlook Profile

If your existing Outlook profile is corrupt or damaged, you may encounter the ‘Unable to expand the folder’ or similar errors. However, you can replace the damaged profile with a new Outlook profile to fix the error.

The steps are as follows:

  • Open the Control Panel and click on User AccountsMail.

Control panel mail settings

  • Click Show Profiles and click the Add button.

mail new Outlook profile settings

  • Enter your new profile name and click OK.

Select the Outlook profile name

  • Enter the email credentials and set up your account under the new profile. Then click Next > Finish.

congratulations message your ccount has been added

  • Select ‘Always use this profile’ in the Mail control panel and then choose your new profile from the dropdown.
  • Finally, click OK and restart the Outlook client.

Repair or Recreate Outlook OST File

With SCANPST or Inbox Repair tool, you can try to repair the OST file. The steps are as follows:

  • Launch ScanPST.exe located in the Microsoft Office installation directory (%programfiles%/Microsoft Office/OfficeXX).
  • Click the Browse button to choose the OST file and click Start.

Microsoft Outlook inbox repair tool

  • After a while, the tool displays the scan results. If errors are found, click the Repair button. This will create a backup copy and start repairing the OST file.

microsft outlook inbox repair tools message ater OST file scanned

Note: The tool may stop responding during the repair process. However, if it doesn’t respond at all, fails, or crashes during the repair process, either the OST is large or severely corrupt. In such a case, recreate the OST file.

Follow these steps to recreate the OST file:

  • Close Outlook 2013, 2016, 2019, or 2021 and go to File > Account Settings > Account Settings.
  • Click the Data File tab.
  • Choose the email account and click Open file location. This opens the default location where Outlook stores the OST file.
  • Back up the current OST file to a safe location and then delete the OST from the default location.   
  • Start Outlook. This will automatically create a new OST file.

After OST file creation, Outlook downloads all the mail folders and items from the server. Check the mail folders and all your emails. If you encounter missing emails or mail folders, convert the backup OST file into PST using Stellar Converter for OST.

After the conversion, you can import the converted PST file into your new OST file via the Outlook Import Export wizard. You can also export the mailbox items from an inaccessible or orphaned OST file to a live Exchange Server or Microsoft 365 directly.


Many Outlook users reported encountering the ‘Unable to expand the folder, Client operation failed’ error, irrespective of the Microsoft Outlook version they are using. This article shares the reasons and solutions to fix the error in Outlook 2021, 2019, 2016, 2013, and 2010. If the error is resolved after creating a new profile or recreating the OST, use the OST to PST converter tool such as Stellar Converter for OST to extract and restore the missing items to your new profile or OST file. The software comes in handy when you encounter errors due to a faulty OST file or need to restore emails from orphaned or inaccessible Outlook OST files.

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Ravi Singh linkdin Icon

Senior Writer at Stellar®. He is an expert Tech Explainer.

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