Offline Storage Table (OST) and Personal Storage Table (PST) files are Outlook data files, which are used to store a synchronized copy of mailbox items, such as emails, calendars, notes, tasks, etc., on the local storage. Outlook for Windows creates an OST file when you sign in using an Exchange, Office 365, or IMAP account.
By default, the OST file is encrypted and bound to the particular Outlook profile in which it is created. Thus, it can't be accessed or imported into other Outlook profiles. However, OST allows authenticated user to access Outlook data, draft messages, create tasks, add notes or contacts, etc., even when the system is offline.
PST or Personal Folder file is created when you sign in to Outlook using a POP3 account. Unlike OST, you can open, access, and import PST files into any Outlook profile, making it an ideal Outlook data file format for backup and migration.
Reasons to Convert OST to PST
There could be several reasons why you may want to convert OST to PST file. Some of them are as follows:
1. OST Integrity Issues
An oversized OST file may get corrupted due to integrity issues, which can lead to errors. You can reduce the OST file size by moving emails and other mailbox items to a PST file. You can also create an Archive (PST file) to store and access older mails.
2. Prevent Data Loss
If you are experiencing errors in Outlook, such as synchronization errors, mails not receiving, etc., you can back up your mailbox data stored in the OST file to PST format. This will help you troubleshoot the Outlook errors safely and avoid any data loss.
3. Synchronization Failure
If your Outlook profile is deleted or disabled from the Exchange server, Outlook stops synchronizing the OST mailbox with the mailbox server. Such OST files are referred to as orphaned OSTs. In such cases, you need to convert the OST file to PST to restore your mailbox data.
4. Exchange Server Failure or Crash
When Exchange or mail server fails or crashes, the OST file may become inaccessible and you may lose access to your OST mailbox items. In such cases, you must convert the OST file to PST to access your mailbox items in another or new Outlook profile.
5. Data Migration
Converting OST to PST helps migrate mail items from one Outlook profile to another. This is particularly helpful if you want to relocate or switch to a different mail server.
Manual Methods to Convert OST to PST Format
Below, we have discussed some free manual methods to convert OST to PST in Outlook 2021, 2019, 2016, 2013, and 2010.
Method 1: Use Outlook Import/Export Wizard
You can convert mailbox items, such as emails, contacts, attachments, journals, calendars, etc., from OST to PST format using the Outlook Import and Export Wizard. This method works when Outlook profile and OST file are accessible and Exchange or Microsoft 365 mailbox is active. The steps are as follows:
In Outlook 2019/2016/2013
- Go to File > Open & Export > Import/Export.
- Choose Export to a file and click Next.
- On the next screen, select Outlook Data File (.pst) and then click Next.
- Select the email profile or folders that you want to export to PST file. Select Include subfolders and click Next.
- Browse and choose a save location on your system to save the PST file. Select 'Allow duplicate items to be created' from the options and then click on Finish.
- After this, a pop-up will appear. You may enter a password to protect the PST file or simply click OK.
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The mailbox items stored in the OST file of your Outlook profile will be converted to a PST file
In Outlook 2010
- Go to File > Open and click on Import.
- From the options, choose Export to a file and then click Next.
- Select Outlook Data File (.pst) and click Next.
- Select the email profile or folders you want to convert to PST. Select the Include subfolders checkbox and click Next.
- Then, click on Browse and select a location on your system or external drive where you want to save the converted PST file.
- Click on Finish. A pop up will appear. You may enter a password or leave it blank and click OK.
Limitations of this Method
- The process can be complex for non-technical users.
- To export large mailboxes, this method may take a significant amount of time.
- There is a risk of incomplete data export, especially for large mailboxes and large emails.
- Users may encounter errors during the export process that may lead to data corruption or loss.
Method 2: Use Outlook Archive Option
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The Archive option in Outlook helps you reduce OST file size and mailbox size on the mail server. You can also use the Archive option as a workaround to move items from the OST file to PST and ultimately, convert OST to PST format. The steps are as follows:
- Open MS Outlook and click on File > Info.
- In Outlook 2010 and 2013, click on Cleanup Tools > Archive. In Outlook 2016, 2019, and 2021, click File > Info > Tools > Clean up old items.
- Select the Archive this folder and all subfolders option. You can select the folder that you need to export to PST (e.g. Sent Items, Inbox, Drafts, etc.).
- Then, enter an appropriate date. Please note that all the mail items that you received till the specified date will be archived to the PST file.
- Click Browse to select a location to save the PST (Archive) file and then click OK.
Limitations of this Method
- Only older emails can be archived.
- Requires manual configuration for each folder.
- Does not include all mailbox items. Only those items deemed as 'old' by the user.
- Large OST files may exceed the size limit of PST files, leading to incomplete archiving.
Method 3: Drag and Drop Emails from OST File to PST
This is an easy way to move a few mailbox items from OST to PST. This enables you to selectively move the emails from online email folders stored in an OST file to a PST file connected to your Outlook account. The steps are as follows:
- In Outlook, click New Items > More Items > Outlook Data File.
- Enter a file name for this PST and click OK. A pop-up appears asking you to enter a password. Click OK to proceed.
- This will add a blank PST file in your Outlook. You can then create folders and move emails or mail items from OST to this PST file. You may also drag and drop the entire folder or subfolder to this PST file.
Limitations of this Method
- This is a time-consuming method and may not export all the metadata or settings to PST. It is recommended to use this method for small batch or specific items you need to convert to PST.
- If Outlook is not starting or you receive an error, you cannot use this method.
- If you try to move several emails at once, Outlook may crash or stop responding.
Method 4: Use OST to PST Converter Software
An OST to PST software comes in handy when you need to convert multiple OST files to PST or when the OST is in the orphaned stage or is inaccessible. One such specialized OST to PST converter software is Stellar Converter for OST. This tool can convert OST files to PST while keeping the folder structure intact. Besides PST, the software allows you to convert the OST to other formats, such as MSG, RTF, HTML, and PDF. You can also export the OST file directly to an Office 365, live Exchange, or existing Outlook account (requires Technician edition).
Following are some prominent features of this advanced OST to PST converter software:
- Converts orphaned, inconsistent, or inaccessible OST file to a usable PST
- Restores mail items, like attachments, tasks, notes, journals, calendar, etc.
- Provides quick preview of mail items
- Supports selective conversion of mail items
- Provides "Find" feature to search OST files on the system
- Options to save emails in different formats, including EML, MSG, PST, RTF, HTML, and PDF
- Provides a self-explanatory and interactive graphical user interface
- Compatible with MS Outlook 2021, 2019, 2016, 2013, 2010, 2007, 2003, 2002, and 2000
The steps to convert OST to PST by using Stellar Converter for OST are as follows:
- Download and install OST to PST converter tool on your Windows PC.
- Click Profile List to choose your OST file or click Choose Mailbox Manually to Browse and select the OST file that you want to convert to PST.
- If you do not know the OST file location, use the Find option.
- After selecting the OST file, click on Convert to begin scan and conversion process.
- After the scan, you can preview all emails and other mail items. Select all the email folders that you want to convert to PST.
- Then, click Save Converted File under the Home tab.
- From the options, choose PST and then click Next.
- Choose a destination path to save the PST file and click OK.
Conclusion
You should always keep an updated backup copy of your Outlook mailbox items, stored in the OST file, in PST format. This can be done by converting the OST file to PST format by using Outlook options. The PST backup will help you avoid loss of mailbox data in case mail server fails, OST file or mailbox gets corrupt, or the profile is disabled/deleted from the mail server.
However, if Outlook is inaccessible and you can't open Outlook, you can use an OST to PST converter software, such as Stellar Converter for OST. The software lets you convert inaccessible or orphaned OST file to PST in a few clicks. You can also convert multiple OST files to PST and split or compact the converted PST file to reduce the file size.
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