Why do I have two Outlook OST files?

Summary: Many Outlook users report having two OST files for the same account in Microsoft Outlook. These OST files get created every time a user logs in to their Outlook account. Multiple OST files may take up sizable space on your laptop/computer and sometimes affect your device’s performance. In this article, let us try to understand the problem of Outlook creating two OST files and see what users can do to resolve this issue.

two Outlook OST files

Offline Storage Table (OST) file plays a crucial role in accessing all emails, meetings, and contact lists from Microsoft Outlook when you are not connected to the Internet or the Exchange server. Thus, it helps you view all the required details in offline mode. The OST file represents the local cache of your Exchange account and works in offline mode. These files are created when you are not connected to the Internet. Once you are connected back, all the changes are synchronized with Exchange server automatically. Therefore, the OST file is of utmost importance to users who are not able to connect to the Internet regularly or facing connectivity issues in their work zone.

While OST files can prove to be the lifeline of a user’s work routine, they can often get stuck in unexpected problems. Like the issue of multiple OST files, for example. Many Outlook users have reported on technical forums that every time they log in to their Outlook application, two OST files are created on their machine. While multiple OST files aren’t an instant concern, this problem with time can slow down the performance of your Outlook and system.

The following are a few possible causes of the Outlook creating two OST files issue.

Reasons why Outlook creates 2 OST files

Some of the possible reasons behind the creation of multiple OST files include:

  • Outlook can create 2 OST files if you have multiple Outlook IMAP profiles configured; for example, one default and one created by you.
  • The second OST file could be an old file or may be associated with a different Exchange account
  • Outlook sometimes generates new OST files when another session has one locked
  • In networked environments, network OST might not be officially supported and thus get corrupted, causing the OST to be created multiple times
  • A user with access to a shared Outlook account could be the reason behind multiple OST files
  • The Outlook profile associated with the OST file is corrupted
  • The locally stored Active Directory (AD) account might be corrupted

Any of the above-mentioned reasons may cause Outlook to create two or more OST files for a single profile. Now let’s see how the users can resolve this issue at their end.

How to resolve the issue?

If you spot more than one OST files on your system and are troubled by the fact that they are occupying much of your disk space, here’s all that you can try out to resolve the issue:

Fix 1: Organize your Outlook profiles

Here are the steps you need to follow:

  • Close all running instances of Outlook
  • Open Control Panel and click on Mail 
  • In the pop-up that opens, click on Show Profiles
  • From the list of profiles, select the profile you would like to remove and click Remove. Then click on Ok. If you have multiple profiles, this would be a good time to narrow them down to one.

Note: If you wish to create a new profile, here are the steps

  1. Once the extra profiles or all profiles have been removed, in the same dialog, click on Add
  2. Type a name for the new Outlook profile and then click on OK
  3. Add an e-mail account to use in your profile by following the instructions on the screen

Fix 2: Backup the data within the OST files and delete the extra ones

If you know which OST is attached to your current profile, you could simply try backing up the data in the extra OST files into your local PST file manually and then delete them.

Fix 3: Repair your Outlook by using Inbox Repair Tool

If none of the previous solutions works, there might be corruption in your Outlook instance or your OST files. To resolve this, run the Inbox Repair Tool, ScanOST.exe, which is the default inbox repair utility by Microsoft.

  • Locate ScanOST.exe in Outlook installation folder on your machine
  • Double-click the executable to launch the utility
  • Follow the instructions to resolve the issue

Fix 4: Use Stellar Converter for OST to export all OST data to PST format

If none of the above methods works, as a final resort, you can convert OST to PST format by using Stellar Converter for OST. This technique also works if your OST file is severely corrupted. All data within it can be safely exported to PST file and then stored on another location or a removable drive (since PST files can be transferred within systems). There are a lot of amazing features this tool comes with, so don’t hesitate in giving it a try.

Wrapping it up

Don’t panic if you see too many OST files on your system. There would be a perfectly logical explanation for such an occurrence. Follow the fixes mentioned above to resolve the “Outlook creating two OST files” issue. If nothing works, use Stellar Converter for OST to convert old OSTs or those belonging to a different account to PST format. Once converted, such files can easily be transferred to another system or secondary storage.

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