Managing the size of your Outlook data file (either a .pst file for POP/IMAP accounts or an .ost file for Exchange/Outlook.com accounts) is important for performance and stability. While you cannot directly set a specific size limit in the traditional sense for existing files, you can significantly reduce the file size through a process called compacting, and manage against potential size limits.
Accessing Your Outlook Data File Settings
To manage the size of your Outlook data file, you first need to access its settings. Follow these steps:
- Navigate to the File tab in Outlook.
- Click on Account Settings, and then select Account Settings again from the dropdown menu.
- In the Account Settings window, click on the Data Files tab.
Here, you will see a list of all data files configured in your Outlook profile. Select the data file you want to manage (either your primary data file or another one you've added).
- Click the Settings button after selecting the data file.
This action opens a dialog box specific to the selected data file type.
Compacting Your Outlook Data File
Compacting your data file is the primary method Outlook provides to reduce its physical size on your hard drive. When you delete emails, contacts, or other items, Outlook marks the space occupied by these items as free, but it doesn't immediately reclaim that space. Compacting cleans up this unused space.
Once you are in the data file settings window (accessed via the steps above), you will typically find a Compact Now button. Clicking this button will start the compacting process. The time it takes depends on the size of the file and the amount of free space within it.
Special Steps for Exchange or Outlook.com Accounts (OST Files)
If the data file you selected in the Data Files tab belongs to an Exchange or Outlook.com account, the process involves an additional step as mentioned in the reference:
- Follow steps 1-4 above (
File > Account Settings > Account Settings > Data Files tab > Select Data File > Settings). - In the properties window that appears for your Exchange/Outlook.com data file, click on the Advanced tab.
- Click the Outlook Data File Settings... button.
This will open a specific dialog for your .ost file where you can find the Compact Now option to reduce its size.
Why Compact Your Data File?
Compacting offers several benefits:
- Improved Performance: Smaller files are generally faster for Outlook to handle.
- Reduced Disk Space: Frees up valuable storage space on your computer.
- Faster Backups: Smaller files mean quicker backup times.
- Reduced Risk of Corruption: Extremely large files can sometimes be more prone to issues.
Managing Data File Size Limits (PST Files)
While compacting reduces the current size, Outlook data files, particularly .pst files, have built-in size limits. In modern versions of Outlook, this limit is very large (typically 50GB), but in older versions, it was much smaller. If your .pst file approaches its limit, you might encounter performance issues or errors.
Compacting helps prevent reaching this limit prematurely by reclaiming unused space. If your file is genuinely large due to the volume of items stored, consider archiving older items or splitting the data into multiple PST files.
Summary of Data File Types
| Feature | .pst File (POP/IMAP) | .ost File (Exchange/Outlook.com) |
|---|---|---|
| Purpose | Stores data locally | Offline copy of mailbox data |
| Primary Action | Compacting, Archiving, Splitting | Compacting |
| Size Limit | High limit (e.g., 50GB+) | Managed by mailbox size limit |
By regularly compacting your data file and being mindful of its overall size, you can help ensure Outlook runs smoothly and efficiently.
