How to Delete an .OST File in Outlook: A Definitive Guide

So, you’re looking to ditch an .OST file in Outlook. Understandable. These offline storage table files can sometimes become bloated, corrupted, or simply unnecessary. Here’s the straight dope: you can’t directly delete an .OST file while Outlook is running and associated with the profile using it. Instead, you need to remove the associated Outlook account. Deleting the account effectively removes the .OST file associated with it. Let me explain how to do it, and why this is the method, before diving into frequently asked questions.

The Nuance of .OST Files: Why You Can’t Just Delete

Before we jump into the “how,” let’s address the “why.” An .OST file is your local replica of your Exchange, Microsoft 365, or IMAP email server. Outlook uses this file to allow you to work offline; emails, calendar events, contacts – it’s all there, synced locally. Deleting it while Outlook is active is akin to pulling the rug out from under a juggler – things will crash. That’s why you must remove the account connection first. This allows Outlook to gracefully handle the “disappearance” of the .OST file.

Step-by-Step: Removing the Account and Associated .OST

Here’s the detailed process. I’m breaking it down into clear, actionable steps.

1. Close Outlook: This is paramount. Ensure Outlook is completely closed – no minimized windows, no tray icon lingering. If needed, use Task Manager (Ctrl+Shift+Esc) to force-quit Outlook.

2. Open Control Panel: There are a few ways to do this depending on your Windows version:

   • Windows 10/11: Search for “Control Panel” in the Start menu.
   • Older Windows: Click Start > Control Panel.

3. Change View By: In the upper-right corner of Control Panel, make sure the “View by” is set to either “Large icons” or “Small icons”.

4. Find “Mail (Microsoft Outlook)”: Scroll through the icons until you find the one labeled “Mail (Microsoft Outlook)”. Click it. This opens the Mail Setup dialog.

5. Show Profiles: In the Mail Setup dialog, click the “Show Profiles…” button.

6. Select the Profile: If you have multiple Outlook profiles, select the one associated with the account whose .OST file you want to “delete”. If you only have one profile, it will be pre-selected.

7. Click “Properties”: With the profile selected, click the “Properties” button.

8. Email Accounts: In the next window, click “Email Accounts…”.

9. Select the Account: In the “Account Settings” window, on the “Email” tab, select the account you wish to remove. This is the account linked to the .OST file you want gone.

10. Click “Remove”: With the correct account selected, click the “Remove” button. Outlook will prompt you to confirm. Confirm your decision.

11. Close the Windows: Close all the open windows – “Account Settings,” “Mail Setup,” and “Mail (Microsoft Outlook)”.

12. Locate and Manually Delete the .OST File (Optional, but recommended): Removing the account usually removes the .OST file. However, it’s a good idea to verify and manually delete it to free up space and ensure complete removal. The default location is usually:

    C:Users[Your Username]AppDataLocalMicrosoftOutlook

    Replace [Your Username] with your actual Windows username. You might need to enable viewing hidden files and folders in File Explorer to see the AppData folder.

    • Show Hidden Files: Open File Explorer, click the “View” tab, and check the “Hidden items” box.

    Find the .OST file that corresponds to the removed account (it will likely be named after your email address) and permanently delete it (Shift + Delete). Be absolutely certain you’re deleting the correct file!

Important Considerations: Data Loss and Backups

Removing an account and its .OST file can potentially lead to data loss if you haven’t properly backed up your data. Here’s what to keep in mind:

• Exchange/Microsoft 365: If you’re using an Exchange or Microsoft 365 account, your data is primarily stored on the server. Removing the account removes the local copy (.OST file), but your data is still safe on the server. When you re-add the account, Outlook will re-sync. However, it’s still prudent to confirm that your crucial data has been properly synced before deleting the .OST file.
• IMAP: With IMAP, your emails are generally synced to the server. However, calendar events and contacts might be stored locally. Double-check your settings and ensure everything is properly synced before proceeding. You can often export these items to a .PST file as a backup.
• POP3: This is where things get tricky. POP3 downloads emails from the server and often deletes them from the server. If you’re using POP3 and you delete the account (and .OST file), you’ll lose those downloaded emails unless you have a backup. Always back up your POP3 data to a .PST file before removing the account.

Frequently Asked Questions (FAQs)

Here are some common questions about deleting .OST files, addressed with my expert perspective:

1. Can I just rename the .OST file instead of deleting it?

Technically, yes, you can rename the .OST file. However, this isn’t recommended as a long-term solution. It might prevent Outlook from accessing the file, but it doesn’t free up the disk space, and it can cause confusion later. Plus, if Outlook tries to access a renamed .OST file, it may cause errors. Simply removing the account is the cleaner and safer approach.

2. What happens if I delete the .OST file while Outlook is running?

Don’t do it! At best, Outlook will crash. At worst, you could corrupt your Outlook profile or even damage your operating system. Close Outlook completely before attempting any .OST file manipulation.

3. How do I find the .OST file if I don’t know where it is?

The default location is C:Users[Your Username]AppDataLocalMicrosoftOutlook. If you can’t find it there, you can use Outlook itself to determine the location before removing the account:

*   Go to **File > Account Settings > Account Settings**. *   Select your email account and click **Change**. *   Click **More Settings**. *   Go to the **Advanced** tab. *   The path to the .OST file will be listed under **Outlook Data File Settings**. 

4. Will deleting the .OST file delete my emails from the server?

Generally, no. If you’re using Exchange, Microsoft 365, or IMAP, your emails are stored on the server. Deleting the .OST file only removes the local copy. However, if you’re using POP3 and have configured Outlook to delete emails from the server after downloading, then deleting the .OST will effectively delete those emails if you don’t have a backup.

5. I deleted my .OST file, but Outlook is still trying to use it!

This usually means that the Outlook profile is still configured to use that .OST file. You need to remove the account from Outlook as described above. Simply deleting the file isn’t enough; you must break the connection within Outlook. Restarting Outlook and even your computer can sometimes help clear cached information.

6. Can I move the .OST file to a different location?

Moving the .OST file manually isn’t supported and can lead to data corruption. Outlook expects the .OST file to be in a specific location. If you need to change the location, you must create a new Outlook profile and configure it to use the desired location.

7. Is it safe to use third-party .OST deletion tools?

I generally advise against using third-party tools for deleting .OST files. These tools can sometimes be unreliable or even contain malware. The method I described above – removing the account from Outlook – is the safest and most reliable way to “delete” the .OST file.

8. How do I prevent .OST file corruption?

Several factors can contribute to .OST file corruption, including sudden power outages, network interruptions, and hardware failures. Here are some tips to minimize the risk:

*   **Use a UPS (Uninterruptible Power Supply):** This will protect your computer from power outages. *   **Ensure a stable network connection:** Avoid working offline for extended periods. *   **Regularly scan for malware:** Malware can sometimes corrupt .OST files. *   **Keep Outlook updated:** Microsoft releases updates to address bugs and improve stability. *   **Use the Scanpst.exe tool:** This tool (located in the Office installation directory) can repair minor .OST file errors. 

9. Can I have multiple .OST files for a single Outlook profile?

No. Each Outlook profile can only have one .OST file associated with each Exchange, Microsoft 365, or IMAP account.

10. How do I back up my Outlook data before deleting the .OST file?

The best way to back up your Outlook data is to export it to a .PST file. Go to File > Open & Export > Import/Export. Choose “Export to a file” and follow the prompts to create a .PST file containing your emails, calendar events, contacts, and tasks. Store this .PST file in a safe location. This is especially important for POP3 accounts.

11. After removing the account, the .OST file is still there. Why?

Sometimes, Windows doesn’t immediately release the file. Try restarting your computer. After restarting, attempt to manually delete the .OST file again. Ensure no other programs are accessing the file.

12. I deleted the .OST file by removing the account, but I want to use the same email address in Outlook again. How do I set it up?

Simply add the email account back into Outlook. Go to File > Add Account and follow the prompts. Outlook will create a new .OST file and sync your data from the server (for Exchange, Microsoft 365, or IMAP). If you backed up your data to a .PST file, you can import it after setting up the account. Remember POP3 users need this backup.

That’s the comprehensive guide. Armed with this knowledge, you can confidently manage your .OST files and keep your Outlook running smoothly. Remember the key is to remove the account, not just haphazardly delete the file! Good luck!