The Outlook Out of Memory or System Resources error usually shows up right when a message won’t open, a reply won’t send, or Outlook simply freezes mid-task. It rarely means the computer is actually low on RAM – more often it points to a corrupted add-in, a bloated data file, or a cluttered profile. This guide walks through the fastest, most reliable fixes in order.
Key Takeaways
- The error is almost always caused by add-ins, a damaged profile, or an oversized data file, not actual low memory.
- Starting Outlook in Safe Mode isolates whether an add-in is the culprit.
- Repairing the Outlook data file with the built-in Inbox Repair Tool fixes a large share of cases.
- Keeping the mailbox and PST or OST file size in check prevents the error from returning.
- A fresh Outlook profile solves stubborn cases that survive every other fix.
Step-by-Step Guide to Fixing the Outlook Out of Memory or System Resources Error
Work through these steps in order. Most people find the problem clears up before reaching the final steps, so there’s no need to jump straight to a profile rebuild.
Start With the Basics
- Step 1: Close Outlook completely, along with any other Office apps running in the background, then restart the computer. This clears temporary memory leaks that build up during a long session.
- Step 2: Check for pending Windows and Office updates by going to Settings, then Windows Update, and separately checking File, Office Account, Update Options, Update Now inside any Office app. Outdated builds are a common trigger for this error.
- Step 3: Reopen Outlook on its own, without launching Word, Excel, or other memory-heavy programs at the same time, and see if the error returns.
Isolate the Add-In Causing the Problem
- Step 4: Close Outlook, then hold the Windows key and press R, type outlook.exe /safe, and press Enter to launch Outlook in Safe Mode. If the error disappears here, an add-in is the cause.
- Step 5: With Outlook open normally again, go to File, then Options, then Add-ins. At the bottom, choose COM Add-ins from the Manage dropdown and click Go.
- Step 6: Uncheck every add-in, click OK, and restart Outlook. Re-enable the add-ins one at a time, restarting Outlook after each, until the error comes back – that add-in is the one to leave disabled or update.
Tip: Third-party add-ins for CRM tools, PDF converters, and antivirus scanners are the most frequent offenders, since they hook into Outlook every time an item opens.
Repair the Data File and Reduce Its Size
- Step 7: Locate scanpst.exe, the Inbox Repair Tool, typically found in a path like C:\Program Files\Microsoft Office\root\Office16. Run it and browse to the PST or OST file listed under File, Account Settings, Account Settings, Data Files.
- Step 8: Click Start to scan the file. If errors are found, click Repair and let the tool finish before reopening Outlook.
- Step 9: Archive or delete old items that are no longer needed, especially large attachments sitting in the Inbox or Sent Items, to bring the data file size down.
Tip: A PST file that creeps close to its size limit slows Outlook down long before it hits the ceiling, so trimming it early avoids this error altogether.
Rebuild the Profile if the Error Persists
- Step 10: Open Control Panel, select Mail, then Show Profiles.
- Step 11: Click Add to create a new profile, follow the setup wizard to reconnect the email account, then set the new profile as the default under ‘Always use this profile’.
- Step 12: Restart Outlook using the new profile and confirm the Out of Memory or System Resources error no longer appears.
Common Problems and Fixes
- Error keeps appearing even in Safe Mode: This usually points to a damaged data file rather than an add-in. Run the Inbox Repair Tool again and check the Windows Event Viewer for related Outlook crash logs.
- Scanpst.exe reports the file is too damaged to repair: Restore a recent backup of the PST or OST file if one exists, or create a new Outlook data file and manually move recoverable items into it.
- Error returns shortly after creating a new profile: The mailbox itself may be oversized or the OST cache settings are too aggressive. Reduce the cached mail period under Account Settings, Change, Offline Settings.
- Multiple Office apps open at once still triggers the error: Available system RAM may genuinely be limited. Close unused programs or check Task Manager for a process consuming unusually high memory.
- Add-ins reinstall themselves after being disabled: Some enterprise add-ins are managed by Group Policy. Check with an IT administrator before attempting to remove them permanently.
Frequently Asked Questions
What actually causes the Outlook Out of Memory or System Resources error?
It’s typically caused by a faulty add-in, a corrupted or oversized PST or OST file, or a damaged Outlook profile, rather than an actual shortage of physical memory on the computer.
Does this error mean the computer needs more RAM?
Rarely. Most cases trace back to Outlook-specific issues like add-ins or data file corruption, so upgrading hardware is not usually the fix.
How can an add-in be confirmed as the cause?
Launch Outlook in Safe Mode using outlook.exe /safe. If the error does not appear, an add-in is very likely responsible, and disabling them one by one will identify which one.
What is the Inbox Repair Tool and where is it located?
It’s scanpst.exe, a built-in Microsoft tool that scans and repairs damaged PST and OST files. It’s usually found inside the Office installation folder under Program Files.
Is it safe to delete old emails to fix this error?
Yes, archiving or deleting unneeded items, especially large attachments, reduces the data file size and often resolves the error without any risk to important messages, as long as archived items are saved first.
How long does repairing a PST file usually take?
It depends on file size, but a typical repair with scanpst.exe takes anywhere from a few minutes to over an hour for very large or heavily corrupted files.
Will creating a new Outlook profile delete existing emails?
No, the mailbox data stays on the mail server or in the existing data file. A new profile simply reconnects to that data with a fresh configuration.
Can antivirus software cause this error?
Yes, some antivirus programs scan Outlook data files or email attachments in real time, which can interfere with Outlook and trigger the same memory-related error.
Should the error be reported to IT support?
If the account is part of a managed work environment and the error persists after these steps, IT support should be involved, especially if Group Policy controls the installed add-ins.
