Learn to Fix the “Cannot Expand the Folder” Error

Megha Sharma
Megha Sharma linkedin | Updated On - December 13, 2022 |

Read time 8 minutes

MS Outlook has become the to-go application for all professionals to prioritize all their email and data management needs. But it is also not immune to technical glitches. Many users have experienced trouble while opening certain PST folders. If you have similar issues where you cannot open or expand the folder in the Outlook application and do not get a way out of this, then reading this blog is a must for you.

We are going the explain the best solutions to fix this error and let you access the folder again to carry on with your work.

The error statement that appears while experiencing this error to access the account mailbox folder is like this-

Cannot expand the folder. The set of folders cannot be opened.

Why does the error “Cannot expand the folder” occur?

This error is common in Outlook 2010 and later versions, to the extent that thousands of users have complained about it. It occurs when an Outlook user attempts to expand the shared folder, public folder, Address Book, or another secondary mailbox from the interface. Instead of expanding the respective folder, the error says:

Cannot expand the folder. The Set of Folders cannot be opened.
Cannot expand the folder. Microsoft Outlook cannot access the specified folder.

Let us know what reasons can be assumed for the occurrence of this error.

Reasons that are responsible for the “Cannot Expand the Folder” error

  • Exchange Cached mode is “ON.”
  • Interference of third-party add-ins
  • Corrupt Outlook profile
  • OST/PST file corruption
  • Microsoft Office application issue
  • Folder Visible permission is not set

Instant Solution

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Top Manual Solutions to Fix “Cannot expand the folder” Error

Try these simple solutions to fix or resolve the “Cannot expand the folder” error on your own.

Solution 1: Make the folder “Visible”
Solution 2: Disable the cached mode
Solution 3: Disable Microsoft Outlook Add-ins
Solution 4: Create a new Outlook profile
Solution 5: Repair the Outlook application
Solution 6: Repair the Outlook database files
Here is the complete explanation of the above-mentioned solutions with their entire process.
Make the folder “Visible”

First, make sure that there are more subfolders than the limit. Earlier, the limit was 5000, but later, Microsoft increased the folder limit. Now, 5000 items per calendar folder and 100000 items per folder are allowed.Then check if the permission for the .Ost folder view is assigned or not.

  1. On the Outlook interface, right-click on the folder that is troubling you and click on the Properties option.
  2. Now, move to the Permissions tab and make sure that “Folder Visible” permission is assigned.
  3. If not, click on the Edit option and assign the same. Click OK to save the settings.
  4. Now, your problem may be resolved.

Disable the Cached Mode

Cached Exchange Mode saves a copy of the mailbox to the user’s computer, and this enables easy access to all the data. But when this mode is on, it may cause trouble in expanding the respective folder due to synchronization issues. It is suggested to disable the cached Exchange mode in Outlook in such a situation. Follow this process to do so-

  1. On your Outlook interface, navigate to File > Account Settings > Account Settings.
  2. Account Settings

  3. Under the Email section, on the Account Settings page, double click on the account causing the issue. Now, it will open the Change Account page. Here, under the Offline Settings section, unselect the Use Cached Exchange Mode option and click on Next to follow the further instructions and save this setting.
  4. Cached Exchange Mode

  5. Now, restart the Microsoft Outlook application and try expanding the folder.

Disable Microsoft Outlook add-ins

Conflicts with the third-party add-ins can affect the synchronization of the mailbox as well as the functioning of the application since they become roadblocks to a smoothly running function. Running the application in the Safe Mode might also help to resolve the issue. You can also try disabling the Outlook add-ins using the following procedure and then attempt to expand the problematic account folder.

  1. On the Microsoft Outlook application interface, click File > Info > Options.
  2. Microsoft Outlook application interface

  3. On the Outlook Options page, click Add-ins. Move to the right panel and then click on the Go option against Manage > COM Add-ins.
  4. COM Add-ins

  5. Now unselect the Add-ins and click on OK.
  6. unselect the Add-ins

  7. Restart the Microsoft Outlook application, and then try expanding the folder again.

Repair the Outlook application

Due to some bugs, errors, or other issues, the application may also get corrupted. Taking it as a solid reason behind this issue, you can try performing an online repair on your Microsoft Office application suite. But before you begin with it, make sure you have a strong network speed to perform this repair. The procedure is as follows-

  1. Go to Control Panel and click on the Programs and Features option.
  2. Move to the installed Microsoft Office program and right-click on it. Select the Change option from the drop-down list.
  3. Select the Change option

  4. Click Yes to continue.
  5. Now select the repair option as Quick Repair and click on Repair.
  6. select the repair option

  7. Follow the next instructions to perform the repair.
  8. Once the repair is completed, try accessing the folder from the Outlook application.

Create a new Outlook profile

A corrupt Outlook profile is another major cause of many problems in Outlook, including this one. All Outlook users can anytime create a new Outlook profile and set it as the default one.This will give you a clean start, and the corruption-containing profile will be deleted for good.

Perform these steps to create a new Outlook profile-

  1. Go to the Control Panel and click on the Mail option.
  2. On the Mail Setup dialogue box, click on the Show Profiles option.
  3. Show Profiles

  4. Click Add to add a new profile. Then provide a name to the Outlook profile and click OK.
  5. add a new profile

  6. Now set this profile to your account by selecting the option saying Always use this profile and then selecting the account from the drop-down list. Then, click on OK.
  7. select Always use this profile

  8. Now launch the Outlook application with this new profile and check if the problem is resolved.

Repair the Outlook Database File

The corrupt .ost file can be a reason for the error, but here you have an advantage that you can anytime recreate the OST file of your configured Exchange Server account. You just require opening the .ost file location from the Account Settings in Outlook and then deleting the problematic .ost file from there using the Delete option simply.

Select Delete option

The default location of the Microsoft Outlook .ost file is given as:


Then restarting the Outlook once would recreate a fresh .ost file without issues. It can resolve your issue if corrupt .ost is the problem.

For users who have corrupted or orphaned .ost files, we recommend the most efficient and secure Kernel OST to PST Converter, which readily recovers data from the corrupt, damaged, or orphaned offline .ost file and allows to save it to the PST file format and more destinations. This tool is suitable for all users, including beginners, and it will get the work done in a jiffy.Get complete information about the tool by visiting its official website.


The error “Cannot Expand the folder” has been witnessed by many Outlook users. The causes behind this might be a lot but can also be resolved without any complications. To begin with, make sure the folders are visible and within the limit range. Then, disable all the add-ins as well as the Cached Mode. A heavily corrupted Outlook profile could be starting other issues as well; hence you can immediately create a new one. In case of corruption in the application or its files, users can always choose to repair those. To get the OST files accurately repaired, you can opt for a professional utility.

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