If you’re an avid Microsoft Outlook user, you may have noticed something puzzling: Outlook seems to create multiple OST (Offline Storage Table) files on your system. This might seem like a minor nuisance, but it can lead to confusion and even performance issues over time.
Creating duplicate OST file for same user is also sign of error within OST file. To figure this out, in this blog post, we’ll explore why MS Outlook creates multiple OST files and how to manage this effectively.
Understanding the Issue
The “Outlook Creating Multiple OST Files” issue refers to the scenario where Microsoft Outlook generates more than one Offline Storage Table (OST) file on a user’s system. OST files are used by MS Outlook to store copies of mailbox data for offline access and synchronization with the mail server when reconnected to the internet.
While it’s normal for Outlook to create one OST file per account, multiple OST files can accumulate over time, leading to confusion and performance issues.
Why Does MS Outlook Create Multiple OST Files?
MS Outlook is creating duplicate .ost files to the same user can be caused due to several factors. Let us understand the causes and reasons why Outlook is creating multiple OST files:
1. Multiple Email Accounts
If you have more than one email account configured in Outlook, each account typically creates its own OST file. This is to ensure that emails and data from each account are stored separately and synced independently. For example, if you have an Office 365 account, a Gmail account, and an Exchange account, Outlook will create a separate OST file for each.
2. Recreating Profiles
Sometimes, you may experience issues with your Outlook profile, such as corruption or synchronization problems. In such cases, you might need to recreate your profile. When you do this, Outlook creates a new OST file for the new profile while keeping the old one. Over time, this can result in multiple OST files, some of which are redundant.
3. Migrating Between Versions of Outlook or Windows
When upgrading to a new version of Outlook or moving from one version of Windows to another, Outlook may generate new OST files during the migration process. If the migration doesn’t fully clean up old OST files, you might find yourself with multiple files that essentially serve the same purpose.
4. Cached Exchange Mode
When you enable Cached Exchange Mode in Outlook, it downloads a local copy of your mailbox in the form of an OST file. If you switch between Cached and Online modes or reset your Cache settings, Outlook might create new OST files for your account.
5. Mailbox Size and Archive Settings
Large mailboxes or the use of Outlook’s AutoArchive feature can also lead to the creation of additional OST files. When AutoArchive is enabled, Outlook moves older items to an archive file (PST), but sometimes, depending on settings or server configurations, it may create additional OST files instead.
6. Multiple User Profiles on the Same System
If multiple users use the same Windows system with different Outlook profiles, each user will have their own OST file. While this doesn’t technically count as “multiple OST files for one user,” it can still contribute to the accumulation of files on a shared machine.
How Duplicate OST Files Can Affect Performance?
While having multiple OST files might seem harmless, it can lead to several issues:
- Slower Performance: Each OST file takes up disk space and processing power, particularly when Outlook tries to sync them. If you have multiple large OST files, this can slow down the overall performance of both Outlook and your system.
- Confusion: With multiple OST files, it can become harder to manage your mailbox and data. You might accidentally access an old or outdated OST file, leading to errors or missing emails.
- Storage Space: OST files can be large, especially if you have many emails, attachments, and calendar items. Multiple OST files can take up significant disk space, which might cause storage problems over time.
How to Manage Multiple OST Files?
If you find yourself with multiple OST files, here are some steps you can take to manage them:
1. Delete Old Profiles
If you’ve created new Outlook profiles over time, check for any old or inactive profiles and delete them. This will remove their associated OST files and free up space.
- Go to Control Panel > Mail > Show Profiles.
- Select the outdated profile and click Remove.
Deleting OST files can help you clear up space and makes it easier for you to manage the data file conveniently.
2. Archive Emails or Use Online Access
If storage space is a concern, consider using Outlook’s built-in archiving feature or accessing older emails online rather than keeping them locally.
- Go to File > Options > Advanced > AutoArchive Settings and configure as needed.
3. Reduce Mailbox Size
Keeping your mailbox lean will reduce the size of your OST file. You can do this by deleting unnecessary emails, especially those with large attachments, and regularly clearing out your Sent Items and Trash folders.
4. Use a Single Profile for Multiple Accounts
If you have several email accounts configured, consider consolidating them under a single profile. This will keep your data organized and reduce the number of OST files.
5. Disable Cached Exchange Mode
In some cases, you can disable Cached Exchange Mode if you don’t need offline access to your mailbox. However, be cautious when doing this as it might impact performance in low-connectivity environments.
- Go to File > Account Settings > Account Settings > Email > Change > Uncheck the Use Cached Exchange Mode option.
6. Manual Cleanup
You can manually delete unnecessary OST files, though it’s essential to ensure the files you delete are not needed anymore. Typically, Outlook stores these files in the following location:
- Windows 10/11:
C:\Users\YourUsername\AppData\Local\Microsoft\Outlook\
7. Repair OST Files
If you notice any corruption in your OST files, you can repair them using Outlook’s built-in repair tool or third-party software. This could also be a reason for Outlook to create multiple OST files every time you open the MS Outlook.
Conclusion
Multiple OST files in Outlook can accumulate for various reasons, from having multiple email accounts to migrating versions or recreating profiles. While this isn’t usually a critical issue, it can lead to performance problems and storage concerns. Managing your OST files by cleaning up old profiles, reducing mailbox size, or consolidating accounts can help you keep Outlook running smoothly.
By understanding the root causes and learning how to manage these files, you can ensure a better Outlook experience and keep your system optimized.
