How to fix “Out of Memory” or a freeze opening a large .msg in Outlook
This happens when a .msg file is too large or heavy for Outlook to load into memory, so it stalls or reports out of memory. It is common with messages that hold thousands of recipients or attachments. Jump to your situation below or work through the methods in order.
By Neeraj Singh ~7 min Updated Jun 2026 91% found this helpful
Error message
Out of Memory or System Resources. Close some windows or programs and try again.
Summary
An out of memory error or a long freeze when opening or copying a .msg file means the message is too big or too complex for Outlook to load at once. The usual culprits are a file packed with thousands of embedded recipients or attachments, very large embedded images, or a 32-bit copy of Outlook hitting its memory ceiling. A damaged .msg can produce the same stall. Start by checking the file size and what it contains, then move to 64-bit Outlook if you are on 32-bit, trim or remove the heavy attachments at the source, and give Windows more virtual memory. If you only need to read the message, a lightweight .msg viewer or converting it to .eml will open it without loading the whole thing into Outlook. Closing other applications frees resources for the attempt.
What this error means
When Outlook opens a .msg it loads the whole message, including every recipient, attachment and embedded image, into memory. If the file is unusually large or complex, that can exhaust the memory available to Outlook, which then freezes or reports that it is out of memory or system resources.
The underlying .msg format does not scale well to extreme sizes, so a message with thousands of attachments or recipients can hit a structural wall. A 32-bit Outlook makes this far more likely because it can only address a limited amount of memory, regardless of how much RAM the PC has.
Common causes
The .msg holds thousands of embedded recipients or attachments.
The message contains very large embedded images or files.
You are running 32-bit Outlook, which has a low memory ceiling.
The PC is low on free RAM or virtual memory at the time.
Many other programs are open and consuming memory.
The .msg file is damaged, which can cause a load to stall.
Windows virtual memory (the page file) is set too small.
Expert insight
“People assume out of memory means the PC is broken, but with .msg files it usually means the file is a monster, a message someone sent to thousands of people, or one stuffed with attachments. The .msg format simply was not built to scale that far. The first real fix is moving off 32-bit Outlook, which runs out of address space long before the machine runs out of RAM. After that I trim the file at the source or just open it in a viewer if all the person needs is to read it. Throwing more RAM at a 32-bit Outlook does nothing, that is the part people miss.”
Manager, Tech Support & Operations · 19+ years fixing Windows and system errors
✓ How to fix it
Method 1
Check the file size and contents
1Right-click the .msg, choose Properties, and note the file size. A message of tens or hundreds of megabytes is the problem.
2If you can open a smaller related copy, look at how many recipients and attachments it carries.
3This tells you whether to trim the file or move to 64-bit Outlook.
Method 2
Use 64-bit Outlook for large files
132-bit Outlook can address only a limited amount of memory and fails on large messages even on a powerful PC.
2Check your version under File, Office Account, About Outlook. If it says 32-bit, install the 64-bit build of Microsoft 365.
364-bit Outlook can load far larger .msg files before running out of memory.
Method 3
Trim heavy attachments at the source
1If you have the original message, remove or save off the largest attachments, then re-save a lighter .msg.
2For a message with thousands of recipients, forwarding it to a single address creates a much smaller file to open.
3Smaller files load well within Outlook's limits.
Method 4
Increase virtual memory and free resources
1Close other open programs to free memory before opening the file.
2In Windows, search for “adjust the appearance and performance of Windows”, open the Advanced tab, then Virtual memory, and let Windows manage a larger page file.
3Restart the PC and try the file again with nothing else running.
Method 5
Open the message in a viewer or as .eml
1If you only need to read the message, a standalone .msg viewer opens it without Outlook loading the whole file.
2Alternatively convert the .msg to .eml, which many apps open more efficiently.
3This avoids the memory wall entirely.
Method 6
Rule out a damaged file
1If a modest-sized .msg still triggers out of memory, the file may be corrupt rather than simply large.
2Save a fresh copy from the original email if you still have it.
3Open the file in a viewer to confirm whether the content is readable at all.
Adding RAM to a 32-bit Outlook does not help, because 32-bit applications can only use a fixed, low amount of memory no matter how much the PC has. Moving to 64-bit Outlook is the change that actually lifts the ceiling. For genuinely huge messages, trimming the file at the source or reading it in a viewer is faster and safer than forcing Outlook to load it.
Frequently asked questions
Why does Outlook run out of memory opening a .msg file?
Because it loads the entire message, including every attachment and recipient, into memory at once. A very large or complex .msg can exhaust the memory available to Outlook and cause it to freeze.
Does adding more RAM fix this?
Only if you are on 64-bit Outlook. A 32-bit Outlook can use only a limited amount of memory regardless of how much RAM the PC has, so the fix is to move to 64-bit Outlook.
How do I open a huge .msg file?
Use 64-bit Outlook, trim the attachments at the source, or open the message in a lightweight .msg viewer or as .eml so the whole file is not loaded into Outlook.
Why would a small .msg cause out of memory?
If a modest file still fails, it is probably corrupt rather than large. Re-save it from the original email, or open it in a viewer to check whether the content is readable.
What makes a .msg file so large?
Usually thousands of embedded recipients or attachments, or very large embedded images. The .msg format does not scale well to extreme sizes.
How do I prevent this?
Keep saved messages reasonable in size, strip heavy attachments before saving, and run 64-bit Outlook so large files have headroom to load.
Still not working?
If the file is too large for even 64-bit Outlook and you cannot trim it at the source, a dedicated .msg viewer or a converter that streams the file rather than loading it whole will let you read or extract the contents. You can also submit your error to us for a tailored fix.
