To delete Outlook data files permanently and free up storage space, you must first close the file within Outlook and then manually delete the .pst or .ost file from your computer using File Explorer. Simply removing the file from view inside Outlook does not delete it from your hard drive.
What are Outlook data files (pst and ost)?
Outlook uses two main types of data files: PST (Personal Folder files) and OST (Offline Outlook Data files). PST files store messages and other Outlook items on your computer and are typically used for POP3, IMAP, and web-based mail accounts, as well as for archiving or backing up data. OST files store a synchronized copy of your mailbox information on your computer and are primarily used for Microsoft Exchange, Microsoft 365, and Outlook.com accounts to allow offline access. PST and OST files are stored in different default locations on your computer, which affects how you locate and delete each type.
Why delete Outlook data files?
There are several common reasons to delete Outlook data files. Freeing up disk space is the most frequent motivation, as these files can grow very large over time. Deleting them can also improve Outlook performance, resolve issues caused by file corruption, and prepare your computer for account migration or a clean start. Additionally, removing old data files helps protect sensitive information and simplifies your email management.
Before you start: close vs. delete
It is crucial to understand the difference between closing a data file and permanently deleting it. Closing an Outlook Data File (.pst) from the Folder pane in Outlook removes it from view but does not delete the file from your computer. The file remains on your hard drive and continues to take up space. Permanent deletion requires you to manually delete the file using File Explorer after closing it in Outlook.
How to permanently delete a pst file
Deleting a PST file is a two-part process. You must first remove it from Outlook, then delete the actual file from your computer.
Step 1: Close the PST file in Outlook
The steps differ depending on which version of Outlook you use.
Classic Outlook: Right-click the file name in the Folder pane and choose "Close 'Outlook Data File'".
New Outlook: To remove a PST file in new Outlook, go to Settings > Files > Outlook Data Files, select 'Manage' on the desired .pst file, and then select 'Close file'.
You cannot remove a PST file if it is set as the default data file. You must first set another data file as default before you can close it.
Step 2: Locate and delete the .pst file using File Explorer
To find the location of a PST file, go to File > Account Settings > Account Settings, select the "Data Files" tab, choose the desired data file, and click "Open File Location". Once File Explorer opens to the correct folder, select the .pst file and delete it permanently.
How to delete an ost file
You cannot delete an OST file from within Outlook while the application is running because Outlook is actively using the file. To delete an OST file, close Outlook completely. Then, navigate to %LOCALAPPDATA%\Microsoft\Outlook in File Explorer. Locate the .ost file associated with your email address and delete it. When you restart Outlook, it will automatically recreate a new OST file and re-download your mailbox data from the server. Deleting an OST file will not result in data loss from the server because OST files are local cached copies of data stored on a mail server.
Troubleshooting common issues
If you receive a 'file in use' error, Outlook may still be running in the background. Ensure Outlook is completely closed before attempting to delete the file. If you encounter permission issues, you may need to contact your system administrator for the required access rights. If a PST file is set as the default data file, you cannot delete it until you designate a different data file as the default. For corrupted files, you can try running the ScanPST tool provided by Microsoft to repair the file before deletion. Deleting an entire Outlook profile via the Control Panel can also remove associated PST files and reset Outlook to a clean state.
Frequently Asked Questions
Are deleted Outlook data files recoverable?
Once you permanently delete a PST or OST file from your computer using File Explorer, it cannot be recovered through Outlook. If you have a backup of the file, you can restore it from there.
What happens to server data when an OST is deleted?
Deleting an OST file removes only the local cached copy of your mailbox. Your emails, contacts, and calendar items remain on the mail server and will be re-downloaded when Outlook recreates the OST file.
How do I delete multiple Outlook data files at once?
You can close multiple PST files from within Outlook by selecting them in the Data Files tab while holding the Ctrl key and then clicking Remove. To delete the actual files from your computer, you must manually select and delete each file in File Explorer.
Can I move PST files to cloud storage to free up space?
Moving PST files to cloud storage services like OneDrive is not recommended and can cause synchronization issues. It is safer to delete unnecessary PST files or archive them to an external drive.
What if I need to delete Outlook data files from my phone?
If you are freeing up phone storage space, Outlook data files are stored on your computer, not your phone. Deleting them from your computer will not affect storage on your mobile device.
