Top 6 Ways to Fix Cannot Expand Folder Error in Outlook

Microsoft Outlook users have faced a particular error over the past decade. It started with Outlook 2010 and users of future versions continue to report it, including Office 365. Users see a pop-up window saying “Unable to expand folder” in Outlook. This happens when expanding a shared folder or a folder in a second mailbox.

How this error persists is unclear, but Office 2019 users seem better off. You can consider switching to this.

Let’s start.

1. File limit

Microsoft Outlook has a limit of 1000 folders. If you have more than the specified number of subfolders, the folder will not expand. This limit applies to Microsoft Exchange accounts. The folder limit is 500 for Outlook 2010, 2013, 2016, and 2019 versions. In addition, the number of items per folder cannot exceed 100,000. Microsoft notes that you may experience performance issues if the limits are exceeded.

2. Disable add-ins

Have you installed add-ins in your Microsoft Outlook account? One or more add-ins can cause a conflict resulting in the Unable to expand folder error in Outlook. Open Outlook in safe mode to eliminate all add-in issues. You can also disable all add-ins without going into safe mode. If the error has disappeared, you will have to reactivate each add-in one by one to check which one was responsible for the error.

5. Create a new Outlook profile

It is recommended to follow point 4 above before proceeding to the creation of a new profile. Rename the folder that you cannot expand in Outlook. Right-click the folder and select the Rename option to do so. Make a backup, if you have to. If you have made a backup on the server or in the cloud, delete the profile mentioned below:

C:UsersUSERNAMEAppDataLocalMicrosoftOutloook

Of course, the above username and drive letter must be your corresponding username and Windows installation drive. Restart your computer.

Open Outlook and under the Files menu, click Account Settings> Manage Profiles.

Click Show Profiles.

Click Add to start creating a new profile.

You can now add email accounts to this newly created profile and check if you still get the Unable to expand folder error.

6. Repair PST and OST files

The Outlook email account data is stored in a .PST file if you are using an IMAP or POP account. The same is stored in an .OST file if you are using Office 365 or an Exchange account. Depending on the email account throwing the Unable to expand folder error in Outlook application, choose a method.

Repair OST file

Open the Control Panel and navigate to User Account> Messaging> View Profiles. Select the profile with which you are having problems and click Properties below. Now select Data files in the following pop-up window.

Select the email account data file and click Open file location.

A new window will open with a file name with the extension .OST. Delete the file and restart your computer. Launch Outlook and it will recreate the file automatically.

Repair PST file

The same steps will not work for the .PST file. Press the Windows key + R to open the Run prompt. Enter the file path below in the case of Office 2016, Office 2019 and Office 365.

C:Program Files (x86)Microsoft OfficerootOffice16

For Outlook 2013:

C:Program Files (x86)Microsoft OfficeOffice15

Double-click the SCANPST.EXE file, which will launch the Microsoft Outlook inbox repair experience. I wish there was a direct way to launch it.

Click Browse in the following pop-up window.

A new File Explorer window will open. You need to locate the .PST file here and when you find it, click the Start button.

Select the option “Make a backup of the scanned file before repair” to create a backup in case of problems.

Now click on Repair to start the process.

Warning

There are far too many versions of Outlook that Microsoft has released over the years. This makes troubleshooting a little more difficult. However, we do our best to offer the best workable solutions. If you’ve found another way to fix the Unable to open folder in Outlook app error, let us know in the comments below.