Summary: Deleting the OST files is often required when Outlook users encounter issues with their Outlook accounts, such as sync errors, delay in sending receiving emails, or OST damage that leads to Outlook errors and prevents a user from accessing their emails. In this article, we discussed step by step process of deleting an OST file safely and recreating a new one while ensuring no email or mail item is lost in the process. This helps you fix common Outlook issues as mentioned earlier and ensure consistent Outlook performance.
Offline Storage Table (OST) is a data file that stores a synchronized copy of mailbox items, such as emails, contacts, attachments, etc., on local storage for quick access. It enables Outlook users to access or read messages even when the system is offline or the network is unreliable.
However, an OST is prone to damage due to one or more reasons mentioned below:
- Outlook or system crash
- Abrupt shutdown or power failure
- Force close Outlook
- Incompatible or faulty add-ins
- Storage media issues
- Malware or virus intrusion
- Network errors
OST may also get damaged or become inaccessible if it grows larger and exceeds the maximum recommended 25 GB limit. As per Microsoft, you should keep Outlook OST file size under 10 GB to avoid performance issues and damage to the file.
However, if you are experiencing issues with Outlook, such as slow load time, delay in sending or receiving emails, Outlook freeze, etc., or encountering OST-related errors, you can delete the file and recreate it. This helps fix the Outlook performance issues and errors.
In this article, you will learn the steps to delete OST to fix Outlook issues or errors without losing a single mail item.
Steps to Delete OST File
It may sound strange but deleting an OST file is not as simple as deleting any other file on your system. It’s a data file that keeps all your mail items, such as emails, contacts, attachments, tasks, calendar items, etc., in one place. If you delete the OST without a backup, you risk losing your mail items.
Thus, it’s important to create a backup before you remove OST from the system. Besides, OST location is not universal. It is based on the Outlook and Windows version you are running on your system.
Below are the steps you can follow to locate, backup, and delete OST to rebuild a new one. However, it’s important to note that Outlook may fail to recreate the OST file if the email account is removed or disabled from the mailbox server.
Step 1: Locate OST File
OST is stored at the default location based on the Windows and Outlook version or edition you have installed. If the MS Outlook is accessible, you can quickly find the OST location by following these steps:
- Open Outlook.
- Right-click on the profile name and choose Open File Location….
- OST location will be displayed in the File Explorer window. This is the default location where OST is stored by Microsoft Outlook.
Alternatively, you can also use Control Panel to open the OST file location. The steps are as follows:
- Access Control Panel and click Mail.
- Click Data Files.
- Select the profile for which you want to locate OST and click Open File Location.
If Outlook is not accessible and displays errors, you need to manually find the OST location. Refer to the below table to know the default locations of OST based on Windows and Outlook versions.
| Windows OS | Outlook Version | OST Location |
| Windows XP | Outlook 2000, 2003, 2007 | C:\Documents and Settings\UserName\Local Settings\Application Data\Microsoft\Outlook |
| Windows XP | Outlook 2010 | My Documents\Outlook Files |
| Windows Vista, 7, 8, 10, 11 | Outlook 2007 | C:\Users\UserName\AppData\Local\Microsoft\Outlook |
| Windows Vista, 7, 8, 10, 11 | Outlook 2010 | Documents\Outlook File\ |
| Windows Vista, 7, 8, 10, 11 | Outlook 2013, 2016, 2019, 2021 | C:\Users\YourUserName\AppData\Local\Microsoft\Outlook |
Some organizations use network storage to store OST files. If you can’t find the OST at any of the locations, contact your IT department or administrator for help.
Step 2: Backup OST File
Once the OST file is located, you must create a backup. There are two ways to back up mail items from the OST file.
- Copy OST to a different location, preferably on another drive partition or external media.
- Export mail items to PST using Outlook Import Export Wizard. You can also export to CSV format or drag and drop emails from Outlook to a folder on Desktop to save the emails as MSG files. However, this doesn’t work if you can’t access Outlook or an error is displayed while opening Outlook.
Step 3: Delete OST File
After creating the backup, you may close Outlook (if running) and then delete OST from the default location. For this, you can right-click on OST and choose Delete. You may also use the Shift + Delete key combination to permanently remove OST from the system.
Alternatively, if the purpose of deleting an OST is to rebuild a new OST, you can rename the old OST file and keep it at the same location. This way, you don’t have to move your old OST file to another drive or partition.
However, if you want to get rid of the damaged or inaccessible OST file, deleting the OST file is what you need to do.
Final Thoughts
After deleting OST when you start Outlook, it creates a new OST file at the same location. It then begins the synchronization process where it downloads the mail items from the mailbox server. Wait for the synchronization to finish. Then check your mail folders and mail items.
If there are missing emails or mail folders, you can still restore them from the backup OST file. However, the OST file cannot be opened or imported directly into Outlook. You need to use an OST to PST converter software, such as Stellar Converter for OST, to convert OST into Outlook importable PST format. The software converts OST into PST with complete integrity and precision while maintaining the folder hierarchy and structure. Besides PST, you may also import the mail items extracted from any OST file to an existing profile on your system, live Exchange Server, or Office 365.
Thank you for reading!