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Summary: Addressing Outlook’s Multiple OST Files Issue: Learn causes and solutions, including managing profiles, manual repairs, and backup strategies. Consider Kernel OST to PST Converter for a risk-free conversion.

Most users prefer to keep their system drive free from unnecessary clutter caused by files and documents. Recently, we encountered a common issue involving Outlook OST files that seem to regenerate even after deletion, occurring each time a user logs into their account. The accumulation of multiple OST files can lead to performance slowdowns in the Outlook application and the overall system.

OST files, short for Offline Storage Table files, serve as local replicas of Exchange Server data stored on the user’s system. These files enable users to access their Outlook data even when they’re offline, without an internet connection. The beauty of OST files lies in their ability to automatically sync and update with the Exchange Server data as soon as an internet connection is reestablished. Therefore, any issue related to OST files can directly impact a user’s ability to access critical elements like emails and contacts when disconnected from the Exchange Server or during network outages. Additionally, these issues can have an indirect impact on the overall system’s performance.

In such scenarios, it’s crucial for users to take immediate action to resolve the problem of multiple OST files and ensure uninterrupted access to their essential data.

Reasons for Multiple Outlook OST Files

Several factors can contribute to the occurrence of multiple OST files, including:

  1. Multiple Outlook IMAP profiles- Outlook generates two OST files when you have set up multiple IMAP profiles, which typically include one default profile and one that you’ve created.
  2. Old or different Exchange account – Another potential cause for the presence of two OST files in Outlook is when the second file is either outdated or associated with a different Exchange account.
  3. Locked session – Outlook may generate new OST data files when an existing session has one locked, resulting in the creation of two files.
  4. Networked environment – In networked environments, OST files are susceptible to corruption, which can trigger the creation of multiple OST files.
  5. Shared Outlook account – The creation of multiple Outlook OST files can also be attributed to a user with access to a shared Outlook account.

Users can encounter this issue in various situations, such as a corrupted Outlook profile, issues with their local Active Directory (AD) account, multiple IMAP account profiles, corruption, or compatibility problems with network OST files. It’s essential to identify these potential causes and then implement the provided remedies for the common problem of ‘Two OST files in my Outlook’ experienced by many users.

Follow these Solutions

If you’d like to address the issue of additional OST file generation every time you log in to the Outlook application, you can follow a series of manual actions or procedures that we will explain step by step.

  • Managing Outlook Profiles
  • Repairing Corrupt OST Manually
  • Backup OST and Remove Extra
Managing Outlook Profiles

To resolve the problem of OST file regeneration, consider removing unnecessary or additional Outlook profiles within the application. Follow these steps after closing your Outlook application (if it’s currently open):

  1. Open Control Panel application in your system with Windows + Run command.
  2. Open Control Panel

  3. Select Mail option and then in the opened Mail Setup dialogue box, click Show Profiles option.
  4. Select Mail option

  5. All the Outlook profiles will get listed. Select the extra or unrequired profiles one-by-one and click the Remove option to remove them.
  6. Select unrequired profiles to remove

  7. Now, delete the extra OST files, logon to the Outlook application and check for two OST files now.
Repair Corrupt OST File Manually

An underlying cause of this issue may be OST file corruption, which you can manually repair using scanPST.exe for various Outlook versions. Below, you’ll find the default path locations for this built-in repair utility in different Outlook versions.

In current Outlook versions (from 2007 to 2019) (64 Bit): C:\Program Files (x86)\Microsoft Office\root\Office xx
In current Outlook versions (from 2007 to 2019) (32 Bit): C:\Program Files\Microsoft Office\root\Office xx
In older Outlook versions (64 Bit): C:\Program Files (x86)\Common Files\System\MSMAPI\<locale ID>
In older Outlook versions (32 Bit): C:\Program Files\Common Files\System\MSMAPI\<locale ID>

You just need to open the application from above folder paths, browse and add the corrupt OST file for repair.

Backup OST and Remove Extra Files

If you’re seeking an alternative solution, the recommended approach is to save the primary OST file as a backup in PST format before removing any additional OST files. When it comes to manual solutions, there are two free methods available for converting OST to PST files: one involving a user-interface approach and another utilizing the archiving feature.

It’s important to note that manual solutions always require a connection to the Exchange Server and may not address orphaned or corrupted OST files adequately. Manual conversion processes also come with limitations such as file size constraints, filtering restrictions, and the risk of data loss.

If you want to avoid these risks and ensure a seamless OST conversion, we recommend using Kernel for OST to PST Converter, one of the most popular tools in this category. This tool simplifies the conversion process by only requiring your OST file and supports conversion to various file formats. Additionally, it offers the option to migrate your OST data to Exchange and Office 365 destinations. Advanced filtering options are available for precise OST to PST conversions.

We encourage you to try out the demo version of the tool to see how it suits your needs before making a final decision.


The OST file plays a crucial role in facilitating connections between Exchange Server and Outlook applications. As such, any issues associated with it, such as the presence of two OST files in Outlook, should be resolved promptly. In this article, we’ve provided solutions that encompass Outlook profile management, OST recovery, OST repair, and conversion methods. Finally, we’ve recommended the best tool for OST conversion.

Q- Will I lose emails if I delete the OST file?

A- Deleting the OST file does not necessarily mean losing all your emails. When an OST file is deleted, the account can still be synchronized with the Exchange Server & this means that users can still retrieve all their Outlook data back.

Q- Why do I have 2 Outlook PST files?

A- Each PST file contains data for a specific email account. If you have more than one email account set up within Outlook, you will have multiple PST files. This is a convenient way to keep your emails organized & easily accessible. 

Kernel for OST to PST