How to Fix “Outlook Data File Reached Maximum Size”

Understanding the PST File and Its Size Limits

A Personal Storage Table (PST) file is the storage system Microsoft Outlook uses to hold your Outlook data.

Each version of Outlook has a limit on PST files, when the PST file reaches the limit, Outlook may block new actions, display error messages, or slow down significantly.

Resolving this requires reducing the file’s size or splitting the PST file into smaller parts to restore normal operation.

Sings of a PST File Reaching Maximum Size

A PST file at its maximum size creates several practical challenges:

• Blocked Functionality: Unable to send or receive emails, add calendar events, or save new contacts until the file size is reduced.
• Slow Performance: Outlook takes longer loading times, search, or display items, affecting efficiency.
• Corruption Risk: Overfilled files are more likely to become corrupted, potentially leading to lost emails or records.
• Size Constraints: Exceeding the limit (20 gigabytes or 50 gigabytes, depending on your version) triggers persistent errors, requiring immediate action.

Addressing this issue promptly ensures uninterrupted access to Outlook and protects your data from potential harm.

Can You Fix a Full PST File Yourself?

Yes, you can resolve the “Outlook data file has reached its maximum size” error using built-in Outlook features and standard computer tools—no additional purchases are necessary. The process is most effective if the PST file is still accessible and hasn’t suffered severe corruption.

This guide presents five DIY methods: deleting unnecessary data, moving items to new PST files, archiving older data, exporting portions of the file, and compacting the PST file to reclaim space. Each method includes detailed steps and solutions for common difficulties, enabling you to regain control of Outlook.

Also Read: How to Reduce OST File Size

5 DIY Solutions for a PST File at Maximum Size

The following methods offer practical ways to reduce or manage a PST file’s size, with clear instructions and fixes for potential obstacles.

Solution 1: Delete Unnecessary Data

Removing unneeded emails, attachments, or junk reduces the PST file’s size directly within Outlook.

• Open Outlook: Launch Outlook and ensure the PST file loads (File > Account Settings > Data Files).

• Identify Large Items: Go to View > View Settings > Sort > Size to list emails by size, or use File > Tools > Mailbox Cleanup > Find items larger than 250 KB.

• Delete Items: Select large or old emails, press Delete, and empty the “Deleted Items” folder by right-clicking it and choosing Empty Folder.
• Clear Junk: Navigate to “Junk Email,” delete irrelevant messages, and empty the folder.
• Check Size: In Data Files > Settings > Advanced, confirm the PST size drops below the limit.
• Test Outlook: Send a test email to verify functionality.

Troubleshooting: If the size doesn’t decrease, compact the file after deletion (see Solution 5) to update the space.

Solution 2: Move Items to New PST Files

This method creates new PST files and transfers data to them, splitting the original file’s contents.

• Start Outlook: Open the program and verify the PST file (File > Account Settings > Data Files).
• Create a New PST: Select Add > Outlook Data File, name it and save it in a folder like Documents.

• Select Data: Choose emails, folders, or contacts to move. Sort by date or sender if needed (View > Sort).
• Transfer Data: Right-click the selected items, choose Move > Copy to Folder, and pick the new PST. Repeat for other segments.
• Monitor Size: Check each PST in Data Files > Settings > Advanced, keeping them under 10 gigabytes.
• Remove Original (Optional): Disconnect the full PST via Data Files > Remove after confirming transfers, keeping it as a backup.
• Troubleshooting: If moving stalls, process smaller batches or restart Outlook to refresh.

Solution 3: Archive Older Data

Archiving shifts older items to a new PST file, reducing the original file’s size while preserving data.

• Access Archive: Go to File > Tools > Clean Up Old Items (or File > Info > Tools > Archive in newer versions).

• Set Parameters: Select the mailbox or specific folders, choose a date, and name the new PST.
• Run Archive: Click OK to move older data to the new file.
• Verify Reduction: Check the original PST size in Data Files > Settings > Advanced. Adjust the date if it’s still too large.
• Access Archive: Open the new PST via File > Open & Export > Open Outlook Data File if needed.

• Troubleshooting: If archiving fails, ensure the file isn’t locked—right-click it in Explorer, select Properties, and uncheck “Read-only.”

Solution 4: Export Portions of the PST File

Exporting specific data to a new PST file removes it from the original, effectively splitting it.

• Initiate Export: Select File > Open & Export > Import/Export.

• Choose Export: Pick Export to a File, then Outlook Data File (.pst), and click Next.

• Select Data: Highlight folders, uncheck “Include subfolders” if desired, and click Next.

• Save File: Specify a location and name, select “Do not export duplicates,” and click Finish.

• Repeat: Export additional folders to separate PSTs, then delete the exported data from the original PST manually (Delete > Empty Folder).
• Confirm Size: Ensure the original PST is below the limit in Data Files.
• Troubleshooting: If export stops, verify free disk space (double the PST size) and retry with smaller selections.

Solution 5: Compact the PST File

Compacting reclaims space from deleted items, potentially reducing the PST size without moving data.

• Open Data Files: Go to File > Account Settings > Data Files.
• Select PST: Highlight the full PST file, and click Settings > Advanced > Compact Now.

1. Run Compact: Let Outlook compress the file this removes space from previously deleted items.
2. Check Size: After completion, review the size in Advanced. Repeat deletion (Solution 1) and compact again if needed.
3. Test: Send an email to confirm Outlook works.
4. Troubleshooting: If compacting doesn’t shrink the file, ensure all deleted items are cleared from “Deleted Items” and “Junk Email” first.

Precautions and Ongoing Management

• Limit Activity: Avoid using Outlook during these processes to prevent data conflicts.
• Backup Data: Copy the PST to an external drive or cloud service (e.g., OneDrive) before starting.
• Monitor Size: Check the PST monthly (Data Files > Settings > Advanced) and act when it nears 75% of its limit (15 gigabytes for older versions, 37 gigabytes for newer).
• Maintain Cleanliness: Regularly delete unneeded emails and compact the file (File > Tools > Mailbox Cleanup) to stay below the limit.

Conclusion

The “Outlook data file has reached its maximum size” error is a common but fixable issue. This guide provides five DIY solutions—deleting data, moving items, archiving, exporting, and compacting—all using Outlook’s built-in tools. Each method includes precise steps and fixes for challenges, empowering users to restore Outlook’s functionality and prevent future problems.