Summary: This article will provide basic understanding of offline Outlook Data File (.ost) also called as Offline Storage Table (OST) file. It will also discuss several issues you may encounter while using an .ost file and how to fix them.
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Outlook uses data files (.ost and .pst) to store mailbox information on your computer. The data files help provide access to your synchronized or downloaded email messages, calendar entries, contacts, and other mail items without an internet connection. Now, let's discuss in detail about the Outlook OST file.
Exchange accounts, IMAP accounts, Office 365 accounts, and Outlook.com accounts use an offline Outlook Data File (.ost) to store synchronized copy of mailbox data on your computer. The file provides access to (previously downloaded) emails, calendar information, contacts, and other data, when connection to the mail server is interrupted.
Essentially, the OST file allows working offline, meaning you can do everything with the mailbox folders in Outlook without network or server connectivity. You can read and compose emails, create appointments, and add contacts. But, you cannot send or receive new messages until the connection gets restored.
When connection is established, changes made to the .ost file are automatically synchronized with the mail server.
When using an OST file in Outlook, keep these points into consideration:
For better understanding of Outlook Offline Data File (.ost), it is imperative to know the difference between OST and PST file.
The OST file is usually located at any of the following locations:
drive:\Documents and Settings\\Local Settings\Application Data\Microsoft\Outlook
If you cannot find the .ost file, follow these steps to find the file:
Step 1:In Outlook, select File.
Figure 1: Select File tab
Step 2: In the window that appears, choose Account Settings, and then click Account Settings.
Figure 2: Outlook Account Settings
Step 3: In Account Settings window, click the Data Files tab and select an .ost file, and then click Open Folder Location.
Figure 3: Open OST File Location
A dialog box displaying the default location of OST file will open.
You may also like to read: How to Change the Location of Outlook OST file?
When using an OST file for Outlook, you may encounter any of the following issues:
When Exchange mailbox connectivity breaks with Outlook for a long time, or you've deleted an old Exchange server without properly backing up the OST file, the file may become orphaned.
An orphaned offline folder (.ost) file means that it has become separate from an Outlook profile or an email account – that was used to create the file.
An OST file can become corrupt due to the following reasons:
You may receive any of these errors when your .ost file turns corrupt:
The Offline Folder (.ost) File becomes inaccessible when it gets orphaned or corrupt.
Here are some troubleshooting steps that can help you resolve OST file problems:
Step 1: Delete OST File and Re-create it
If an OST file in Outlook has turned corrupt or is inaccessible, try deleting the file and get a fresh copy by downloading it from the mail server. Once you know the location of Offline Folder (.ost) file, you can easily delete it. To delete the file, browse the location where it is stored. Find and select the .ost file with errors, and delete it.
Once the deletion process is complete, open Outlook and it will automatically create a new .ost file. But, if it doesn't re-create the file, here's how you can do it:
Figure 4: Account Settings Window
Figure 5: Change Account Window
Figure 6: Microsoft Exchange Advanced Settings
Figure 7: Outlook Data File Settings
Step 2: Create a New Outlook Profile
Sometimes, creating a new Outlook profile can help you resolve the OST file related issues.
Steps to create a new profile are as follows:
NOTE: If you want to use an existing .ost file, make sure to copy the existing file to a new location.
Figure 8: Control Panel Items
Figure 9: Mail Setup Window
Figure 11: New Profile Window
Figure 12: Add Account Window
Figure 13: Change Account Settings
Figure 14: Server Settings Window
Figure 15: Outlook Data File Settings
Figure 16: Browse OST File
Figure 17: New Outlook Data File Window
Figure 18: New Profile Added
After successfully executing the steps, open Outlook again to recreate the .ost file for the account you want to repair.
Step 3: Use Stellar Converter for OST Software
Stellar Converter for OST software can help you extract data from an orphaned, inaccessible .ost file, by converting the file to .pst file format. OST to PST Converter can convert multiple OST files to PST format in a single process.Why You Should Use Stellar Converter for OST?
Question. Can I open OST file without an Exchange account?
Answer. No.You cannot open an OST file without an Exchange account. However, Stellar Converter for OST can help you open the Offline Outlook Data files without an Exchange account.
Question. When trying to open an .ost file, am getting this error "The file.ost cannot be accessed because it has been configured for use with a different mailbox"? How can I fix this error?
Answer. You may encounter this error if you are trying to open the OST file on a different machine. But, if you are attempting to open an old OST file on the same machine used for creating that file, try these tips to fix the error:
Question. Can I manually convert my OST files to PST files?
Answer. Yes.You can use the Outlook built 'Import/Export' wizard to manually convert OST files to PSTs. But for manual conversion, you must be connected to Exchange server and have Outlook installed on your computer.
In this guide, you can find different methods to retrieve emails from an Offline Outlook Data File (.ost). In addition, based on these scenarios, we have also explained how to recover emails from an OST file manually or by using a powerful tool.
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