When using Microsoft Outlook, you may encounter the frustrating error message: “Out of memory or system resources. Close some windows or programs and try again.” This issue often causes Outlook to freeze, crash, or fail to open emails, folders, and attachments—even on PCs with plenty of RAM.

The root cause usually lies in oversized Outlook data files, too many add-ins, corrupted profiles, or limitations in Windows system settings. The good news is that with the right fixes, you can restore Outlook’s performance and prevent these errors from returning.

In this guide, we’ll walk through proven solutions to fix Outlook’s “Out of Memory” error, step by step.

1. Remove Unnecessary Outlook Data Files and Profiles

Too many connected PST/OST files or unused profiles can overload Outlook’s memory usage. Cleaning them up helps Outlook run more efficiently.

Steps:

1- Open Outlook > File > Account Settings > Account Settings.

2- Go to the Data Files tab. Review the list of PST/OST files.

3- Select files you don’t need and click Remove to disconnect them.

4- To remove old profiles, go to Control Panel > Mail > Show Profiles, then delete unused ones.

Reducing the number of files and profiles decreases memory consumption, especially during startup.

2. Repair Corrupted Outlook Data Files

A corrupted PST or OST file can cause Outlook to use unnecessary resources. Repairing these files can resolve hidden errors.

Steps:

1- Close Outlook completely.

2- Locate ScanPST.exe (Inbox Repair Tool) in your Office installation directory (e.g., C:\Program Files\Microsoft Office\root\OfficeXX\).

3- Open ScanPST.exe > Browse > select your PST/OST file > Start.

4- If errors appear, click Repair.

5- Restart Outlook and check if the error persists.

3. Reduce Outlook Cache Size via Registry Editor

If Outlook’s cache grows too large, it may trigger resource exhaustion. Adjusting cache settings in the Registry can help.

Steps:

1- Close Outlook.

2- Press Windows + R, type regedit, and press Enter.

3- Navigate to:
HKEY_CURRENT_USER\Software\Microsoft\Office\XX.X\Outlook\PST
(Replace XX.X with your Outlook version, e.g., 16.0 for Outlook 2016).

4- Right-click the right pane > New > DWORD (32-bit) Value > name it UseLegacyCacheSize.

5- Set its value to 1.

6- Restart your PC.

This forces Outlook to use a legacy cache size that’s less memory-intensive.

4. Optimize System and Virtual Memory Settings

Outlook relies not just on physical RAM but also on virtual memory (paging file). Increasing virtual memory ensures smoother performance.

Steps:

1- Right-click This PC > Properties > Advanced system settings.

2- Under the Advanced tab > Performance > Settings.

3- In the new window, go to Advanced > Virtual memory > Change.

4- Uncheck “Automatically manage paging file size.”

5- Select your system drive, then set Custom size (e.g., 4096 MB minimum and maximum for 4GB RAM, higher for modern systems).

6- Click Set > OK, then restart your computer.

5. Disable Problematic Add-Ins

Add-ins can be helpful, but poorly coded or resource-heavy ones often cause Outlook crashes.

Steps:

1- Press Windows + R, type Outlook.exe /safe, and press Enter (launches Safe Mode).

2- Go to File > Options > Add-ins.

3- At the bottom, select COM Add-ins > Go.

4- Uncheck all add-ins > restart Outlook normally.

5- Re-enable add-ins one by one until you find the problematic one.

6- Disable or uninstall faulty add-ins permanently to avoid future errors.

6. Update Outlook and Windows

Microsoft frequently releases patches that improve stability and memory management. Keeping your system up to date can prevent recurring issues.

Steps:

1- In Outlook, go to File > Office Account > Update Options > Update Now.

2- In Windows, open Settings > Update & Security > Windows Update > Check for updates.

3- Install all updates and restart your computer.

7. Increase the GDI Object Limit (Advanced)

Outlook uses GDI (Graphics Device Interface) objects for rendering UI elements. If the limit is too low, Outlook may run out of system resources.

Steps:

1- Press Windows + R, type regedit, and press Enter.

2- Navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows

3- Look for GDIProcessHandleQuota. If it doesn’t exist, create a new DWORD (32-bit) value with that name.

4- Set its value to 20000 (decimal).

5- Restart your PC.

This increases the GDI limit and helps Outlook handle larger workloads.

Final Thoughts

The Outlook “Out of memory or system resources” error can be disruptive, but it’s usually fixable with the right steps. From reducing data files and repairing corrupted PSTs to optimizing system memory and disabling faulty add-ins, these fixes will restore Outlook’s performance and stability.

If the problem persists even after applying all solutions, consider creating a new Outlook profile or reinstalling Office as a last resort. By maintaining a lean Outlook setup and keeping Windows updated, you can prevent resource issues from slowing down your productivity.