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10 Tech How-To

Outlook Error Not Enough Memory: Fixes That Work

Guide 10-13806 · Updated · Step by step

If Outlook shows an “not enough memory” error, it usually means the program has run out of available system resources, not that your computer’s RAM is physically full. The fix is to close other programs, clear Outlook’s cache, disable add-ins, or repair the data file, in that order.

Why Outlook Says “Not Enough Memory”

Outlook is a 32-bit application by default, which means it can only use about 2 GB of memory (RAM) no matter how much is installed on your PC. When your mailbox grows large, or you have many add-ins, Outlook hits that 2 GB ceiling and throws the error. This is a hard limit built into the program, not a sign that your computer is broken.

Other common triggers include:

  • Too many Outlook items (emails, calendar entries, tasks) in one folder
  • Large attachments or embedded images in emails
  • Corrupted navigation pane or search index
  • Third-party add-ins that leak memory
  • Running Outlook alongside other memory-hungry apps like Chrome or Excel

Quick Fixes to Try First

  1. Close other programs – especially web browsers with many tabs, video editors, or other Office apps. This frees up system memory for Outlook.
  2. Restart Outlook – a simple restart clears temporary memory leaks.
  3. Restart your computer – this clears the system’s memory and resets all processes.
  4. Run Windows Update – sometimes a pending update causes instability.

Clear Outlook’s Cache and Search Index

Outlook stores a lot of temporary files and a search index that can grow corrupt. Clearing them often resolves the error.

  1. Close Outlook completely.
  2. Press Windows + R, type %localappdata%\Microsoft\Outlook and press Enter.
  3. Delete the contents of the RoamCache folder inside that directory.
  4. Restart Outlook. It will rebuild the cache.

If the error persists, rebuild the search index:

  1. Go to File > Options > Search in Outlook.
  2. Click Indexing Options.
  3. Click Advanced > Rebuild and confirm.

Disable Problematic Add-Ins

Add-ins are a leading cause of the “not enough memory” error because they run inside Outlook and consume memory. To disable them:

  1. In Outlook, go to File > Options > Add-ins.
  2. At the bottom, select COM Add-ins from the Manage dropdown and click Go.
  3. Uncheck all add-ins except the Microsoft ones (like Outlook’s own).
  4. Click OK and restart Outlook.

If the error goes away, re-enable add-ins one by one to find the culprit.

Repair Your Outlook Data File

The error can also come from a corrupted .pst or .ost file. Outlook includes a repair tool called Scanpst.exe (Inbox Repair Tool).

  1. Close Outlook.
  2. Navigate to C:\Program Files\Microsoft Office\root\Office16 (or wherever Office is installed).
  3. Run Scanpst.exe.
  4. Click Browse to select your data file. The default location is %localappdata%\Microsoft\Outlook.
  5. Click Start and let it scan and repair.

For .ost files, you can also delete the file and let Outlook recreate it from the server – but only if your account is IMAP or Exchange. For POP3, you must back up your .pst first.

Switch to 64-Bit Outlook

If you have a 64-bit version of Windows and Office 2016 or later, you can install the 64-bit version of Outlook. This removes the 2 GB memory limit and is the most permanent fix for large mailboxes.

To check your current version: File > Office Account > About Outlook. If it says 32-bit, you can download the 64-bit version from your Microsoft account or through your Office installer. Note that 64-bit Outlook cannot load legacy 32-bit add-ins, so test your add-ins after switching.

Prevent the Error from Returning

  • Keep your mailbox under 10 GB if possible – archive old emails to a separate .pst file.
  • Empty the Deleted Items folder regularly.
  • Disable unused add-ins permanently.
  • Use the Mailbox Cleanup tool (File > Tools) to find large items.
  • Update Outlook regularly to get memory leak fixes.

Frequently Asked Questions

Does “not enough memory” mean I need to buy more RAM?

Usually no. Outlook’s 32-bit limit is the real bottleneck, not your physical RAM. Even with 16 GB of RAM, Outlook can only use about 2 GB. The fixes above address the software side first.

Why does the error happen with a small mailbox?

Sometimes a small mailbox still has a corrupted search index or a bad add-in. Also, if you have many folders or rules, those can consume memory. Try clearing the cache and disabling add-ins.

Will deleting my .ost file lose my emails?

No, if your account is IMAP or Exchange, the .ost is just a local cache. Outlook will recreate it from the server. But for POP3, the .ost is your only copy – do not delete it without exporting to a .pst first.

Can I increase the memory limit for 32-bit Outlook?

No, the 2 GB limit is hard-coded in the 32-bit version. The only way to go beyond it is to switch to 64-bit Outlook.

What if none of these fixes work?

Try creating a new Outlook profile (Control Panel > Mail > Show Profiles > Add). If that fails, repair Office from Settings > Apps > Microsoft Office > Modify > Repair. As a last resort, reinstall Office.

Related

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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