The most common cause is a bloated or oversized PST file. Additional triggers include sync failures or corrupted data files. Now that you know the causes, let’s discuss the solutions.
1. Compact the PST File
Outlook allows you to reduce the size of your PST file by compacting it. Normally, when you delete emails, the file size isn’t reduced immediately—compacting manually can help free up space. Note: Offline Outlook Data Files (.ost) cannot be compacted directly.
2. Update Outlook/Office
Microsoft frequently releases updates to improve Outlook and fix bugs. If your Outlook error is due to a known issue that’s been patched, updating should fix it.
3. Use Online Mode
Outlook operates in either Online Mode or Cached Mode. If you’re getting the error in cached mode, switching to online mode may help.
4. Repair Outlook’s PST File
Outlook stores your email data in a PST file. If this file is corrupted, Outlook can fail. Luckily, Microsoft provides a tool called SCANPST.EXE to fix PST files. The location of your PST file may differ based on your Outlook and Windows version.
5. Empty the “Deleted Items” Folder
Since this error can be caused by storage issues, make sure that your Deleted Items folder isn’t using up unnecessary space. To empty the Deleted Items folder automatically:
6. Delete Unnecessary Emails
Lots of old or junk emails can quickly fill up your Outlook data file. Also, every forwarded email is saved in both your Inbox and Sent Items by default, using extra space. Deleting unnecessary or duplicate emails—and removing large attachments—can help. To stop saving a copy of forwarded messages automatically:
7. Run the Mailbox Cleanup Tool
Outlook’s Mailbox Cleanup helps you identify and manage large emails, which can free up a lot of space.
8. Use Outlook’s Import/Export Feature
The Import/Export wizard allows you to move or split PST files, helping to reduce their size.
9. Use the “Move to Folder” Option
Outlook’s Move to Folder feature helps you easily transfer emails from your main PST file to another, reducing its size.
10. Use Outlook Archive Wizard
Old emails can fill up your PST file over time. Using the Archive Wizard lets you move older items to a different file.
11. Create a New Outlook Data File
If your current Outlook data file is corrupted, making a new one and setting it as default may solve the error.
12. Increase Maximum Storage Size of Outlook PST File
Microsoft sets a default limit for PST files, but you can manually increase this using the Windows Registry. Warning: Be very careful when editing the Windows Registry; incorrect changes can harm your system.
13. Run Microsoft Support and Recovery Assistant
The Microsoft Support and Recovery Assistant can automatically diagnose and fix many Outlook issues. If it can’t fix the problem, it will guide you on what to do next.
