5 Fixes for Microsoft Outlook Out of Memory or System Resources Error on Windows

Quick Tips

• Several factors can affect Microsoft Outlook’s performance on Windows, such as the amount of available RAM, the size of your mailbox, and the number of data files.
• Try removing unwanted Outlook PST files to see if that helps.
• You can run Microsoft’s Office repair tool to fix most problems with Outlook, including this one.

Fix 1: Run the Inbox Repair Tool

Damaged or corrupted PST or OST files can cause Outlook to run out of memory on your Windows computer. Fortunately, Microsoft Outlook includes a tool that automatically repairs your data files. Here’s how to run it.

Step 1: Press the Windows key + E to open File Explorer and navigate to the following folder.

C:\Program Files\Microsoft Office\root\Office16

Step 2: Double-click the SCANPST.EXE file.

Step 3: Click Start to initiate the scan.

Step 4: Click on Repair if the tool finds any issues.

Fix 2: Remove Unwanted Outlook PST Files

Too many PST files, especially large ones, can affect Outlook’s performance and cause it to display the “Out of memory or system resources” error on Windows. To avoid this, consider removing unnecessary PST files using these steps:

Step 1: Press the Windows key + R to open the Run dialog box. Type control in the text field and press Enter.

Step 2: Change the view type to Large icons and select Mail (Microsoft Outlook).

Step 3: Click the Data Files button.

Step 4: Select the PST file you don’t need and click on Remove.

Fix 3: Reduce Memory Cache Size for Outlook Data Files

If you don’t want to delete any Outlook PST files, you can reduce the memory cache size for those data files to fix the problem. Here’s how to go about it.

Step 1: Close the Outlook app on your PC. Click the search icon on the taskbar, type registry editor, and select Run as administrator.

Step 2: In the Registry Editor window, paste the following path in the address bar at the top and press Enter.

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST

Step 3: Right-click on the PST key, go to New, and select DWORD (32-bit) Value. Name it UseLegacyCacheSize.

Step 4: Double-click the UseLegacyCacheSize DWORD and change its value data to 1. Then, click OK.

Fix 4: Increase the Size of the Memory Heap

Another thing you can do is increase the size of the memory heap for Microsoft Outlook, which will allow the program to use more memory during runtime. This process also requires you to edit registry files, so follow the instructions carefully.

Step 1: Open Registry Editor using the search menu.

Step 2: Paste the following path in the address bar at the top and press Enter.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem

Step 3: Right-click on the Windows Messaging Subsystem key > go to New > select DWORD (32-bit) Value. Name it SharedMemMaxSize.

Step 4: Double-click the newly created DWORD. Type 300000 in the value data field and click OK.

Step 5: Right-click on the Windows Messaging Subsystem key, go to New, and select Key. Name it Applications.

Step 6: Right-click on the Applications key, go to New, and select Key. Name it Outlook.

Step 7: Right-click on the Outlook key, go to New, and select DWORD (32-bit) Value. Name it SharedMemMaxSize.

Step 8: Double-click the SharedMemMaxSize DWORD, type 300000 in the value data field, and click OK.

Fix 5: Run the Office Repair Tool

If all else fails, run the Microsoft Office Repair tool to fix Outlook’s “Out of memory or system resources” error.

Step 1: Press the Windows key + R to open the Run dialog box. Type appwiz.cpl in the box and press Enter.

Step 2: In the Programs and Features window, select the Microsoft Office product on the list and click the Change button at the top.

Step 3: Select Online Repair and click Repair.