Offline Storage Table (OST) and Personal Storage Table (PST) are Outlook data files which are used to store a synchronized local copy of mailbox items such as emails, calendar, 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 that you are signed in. Thus, it can't be accessed or imported into other Outlook profile. However, OST allows authenticated user to access Outlook account, draft messages, create tasks, add notes, contacts, etc., even when the system is offline. All changes made to Outlook are stored in the OST file which gets synchronized with the mailbox server as soon as the system connects to the internet.
PST, also known as Personal Folder file, is created when you sign in to Outlook using a POP3 account. Unlike OST, one can open, access, and import PST files to any Outlook profile, which makes it an ideal Outlook data file format for backup and migration. And that's one important reason why you may want to convert an OST file to PST.
Other Reasons to Convert OST to PST
1. OST Integrity Issues
An oversized OST file becomes prone to corruption due to integrity issues. You can reduce the OST size by moving older emails and other mailbox items to a PST folder. You can also create an Archive to store and access these mails on your local machine.
2. Prevent Data Loss
If you are experiencing errors in Outlook such as sync errors, mails not receiving etc., you should back up your mailbox data stored in the OST file to PST. 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. This may also happen due to security-related issues. Such OST files are referred to as orphaned OST. In such cases, you must export the mailbox items in the OST file to PST to safeguard your mail data.
4. Exchange Server Failure or Corruption
When Exchange or mail server fails or crashes, OST file may become inaccessible and you may lose access to your mailbox items. In such cases, you must convert the OST file to PST to access your mailbox items from other or new Outlook profile.
Problems Related to OST to PST Conversion
An OST file is bound to the MAPI profile and encrypted by default. So, if you have an orphaned or inaccessible OST file that you want to convert to PST, you cannot do so as you cannot access or convert OST file to PST directly from any other Outlook profile.
Microsoft doesn't provide any OST to PST converter tool either. In such cases, the only way to convert OST file to PST is by using a specialized OST to PST converter software. Refer to Method 3.
Here are all the possible ways to convert OST to PST in Outlook 2019, 2016, 2013, and 2010.
Free Steps to Convert OST to PST
Step 1: Use Outlook Import/Export Wizard
This requires access to Outlook. You can choose to convert selected or all email folders in OST to PST format.
In Outlook 2019/2016/2013
- Click 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 duplicates to be created' from the option 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'.
The mailbox items stored in the OST file of your Outlook profile will be converted to a PST file.
In Outlook 2010
- Open Outlook 2010 and 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 Include subfolders checkbox and click Next
- Then click on Browse and select 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
Step 2: Use Outlook Archive Option
Archive option helps you reduce OST file size which cuts the mailbox size on the mail server. Thus, it helps you avoid errors caused by mailbox size limits.
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 and 2019, click File > Info > Tools > Clean up old items
- Select 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 a PST file
Step 3: Drag and Drop Emails in OST file to PST
This is an easy way to move a few mailbox items to PST whenever you want to. This enables users to dynamically move the emails from online email folders stored in OST file to an offline 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 file and click 'OK'. A pop up appears where you can enter a password. Click 'OK' to proceed
NOTE: If you enter a password, you will have to enter it every time you want to access the PST or when Outlook starts.
- This will add a blank PST file in your Outlook. You can then create folders and move emails from mail items in OST to this PST file. You may also drag and drop the entire folder or subfolder to this PST file.
These mails will be stored offline on local storage and help you reduce the mailbox size on server and OST file, thereby saving the OST from corruption. However, this takes a lot of time and if you try to move several emails at once, Outlook may crash or stop responding.
NOTE: The above steps will help you convert OST to PST only if the Outlook is accessible. If Outlook is not starting, you must follow the next step to convert OST to PST.
Step 4: OST to PST Converter Software
An OST to PST software comes handy when you need to convert multiple OST files to PST. Also, when the OST is in orphaned stage or inaccessible due to sync error or profile deletion from the Exchange server.
However, a specialized OST to PST converter tool such as Stellar Converter for OST can convert OST file to PST in a few clicks. Besides PST, the software allows you to convert the OST to other formats such as MSG, RTF, HTML, & PDF. You can also export the mailbox items in OST directly to an Office 365, Live Exchange, or existing Outlook profile (requires Technician Version).
The steps are as follows:
- Download and Install OST to PST Converter tool on your Windows PC
- Click Browse and select the OST file that you want to convert to PST
- If you do not know the OST file location, click on Find
- 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 'Home' tab
- From the options, choose PST and then click 'Browse'
- Choose a destination path to save the PST file and click 'OK'
NOTE: The software lets you convert a few mailbox items in OST to PST for free. If you want to convert all mailbox items, you must activate the software by using a valid activation key.
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 Exchange fails, OST file or mailbox gets corrupt, or your profile is disabled/deleted from the mail server accidentally.
However, if the 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 an inaccessible or orphaned OST file to PST in a few clicks. You can also convert multiple OST files to PST and split or compact exported PST files.