Top 4 Methods to Convert OST to PST

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An OST file (.ost) is the file format associated with Exchange Server accounts. This file contains mailbox data including email messages, calendars, and tasks. If this critical data file cannot synchronize with the server, it must be converted to PST to recover access to its contents. Read this resource to understand how to convert OST to PST without Outlook for free.


The mailbox data management of Microsoft depends on its two file formats: OST and PST. An offline storage table (.ost), file allows users to operate offline, with changes instantly synced when Internet connectivity is restored. However, the PST, or personal storage table (.pst) file, is used to save user Outlook data for POP3, IMAP, and web-based email accounts. In other words, OST files save data obtained from an offline Exchange Server, whereas PST files store data in personal folders. Both file formats serve to maintain the mailbox up to date with new emails, meeting requests, delivery reports, and so on.

However, in some circumstances, it is necessary to import OST into PST files. In the event of a server crash, we must convert OST to PST in order to access and restore mailbox contents. Similarly, when deleting profiles or migrating accounts, an OST to PST conversion is required. In this resource, we will discuss the benefits of converting OST to PST. Stay tuned to this guide to learn how to convert OST to PST without Outlook free.

Reasons to Convert OST files to PST format:

We need to import OST into PST files because of the following reasons:

  • In the event of Exchange Server crash, when we need to access mailbox data, we need to convert OST files to PST.
  • Users need to import OST files to Outlook to access them during server downtime and maintenance.
  • When the Outlook user wishes to recover mailbox data on the Exchange Server.
  • Users need to convert OST files to PST when OST files become inaccessible owing to corruption.
  • In the case of migrating from one email client to another and the new email client doesn’t support OST files.

How to Convert OST to PST Using Outlook?

Converting OST to PST is a bit challenging. To start the process, first log in to Outlook using the same Exchange profile. Select any of the following methods to start the conversion process:

Method 1

Using the Import/Export Wizard: First login to the Outlook with the Exchange account that was used to create the OST files and then follow the below instructions to export the OST mailboxes into PST format.

  • Go to Files >Open & Export and click Import & Export.
  • Select Export to a file, then click Next
  • Select the Outlook Data File (.pst) option, then proceed to Next.
  • Select the targeted folder you need to export and click Next. You can include the subfolders as well.
  • Browse the location where you want to save the new PST files and select Replace duplicates with items exported. Click on Finish.

Method 2

Using the Archiving Method: Microsoft Outlook provides a facility to save the OST file items in a separate PST file. This method ensures better mailbox optimization as the user move older messages in the archive folder. Follow the below instructions to initiate the archiving process:

  • Explore the MS Outlook application.
  • Hit on the ‘File’ menu and click ‘Archive.’
  • A screen will appear, choose the desired File or Folder that needs to be archived.
  • Navigate to the location where the archived file is to be saved.
  • Now, click on ‘Finish’ to end the process.

Method 3

Drag and Drop Mailbox Items: This is another method of converting OST to PST. Follow the below steps to initiate this process:

  • Login to your email profile in the Outlook app.
  • Pick the emails you want to retrieve from the email folder, hold down the Shift key to select multiple emails.
  • Drag and drop the selected emails onto the destination Folder where you want to save the extracted emails.
  • All the selected emails are retrieved and saved as individual.eml files format.

Method 4

Convert OST to PST using Stellar Converter for OST

In this part of the post, we will discuss how to extract emails from Outlook using a professional OST to PST converter tool. Using tools like Stellar Converter for OST is an effective way to retrieve emails from an OST file. The most exciting factor of this software that can catch the fancy of any Outlook user is that anyone can download its Free Version to test its performance. Featuring a user-friendly interface and advanced filter options, this software quickly converts large OST file to PST files. It is quite helpful in cases when the Exchange Server crashes or is inaccessible.

Salient Features of Stellar Converter for OST:

  • Free trial download with no file size limitation
  • Free Demo Version prompts users to preview all the converted file data
  • Available in 3 versions—Corporate, Technician, and Toolkit to choose from
  • Converts All Offline Mailbox items with Free Preview
  • Auto-splits large PST files while saving the mail items
  • Saves the mailbox data in PST, EML, MSG, RTF, HTML, and PDF file formats
  • Converts multiple OST files in a batch, Compacts & Splits PST file, Migrate to Microsoft 365—Technician Version
  • Repairs corrupted PST file, Recovers the mailbox items, Merges multiple PST files—Toolkit Version


In the above post, we have discussed in length about Outlook’s Offline Storage Table (.ost) file format. We have learned that OST files can save data from IMAP, Exchange, Office 365 and Outlook accounts and stores mailbox data such as email messages, calendars, and tasks. We have also explored reasons where OST to PST conversion is required. Those factors include Exchange Server crash, server maintenance & downtime, OST file corruption, etc.

The above post also discussed 3 methods– Import/Export Wizard, Archiving, and Drag & Drop Methods to convert OST to PST using Outlook. In addition to this, we have also explored a professional method using OST to PST converter tool like Stellar Converter for OST. Stellar’s OST to PST conversion speed makes this software a hit among IT admins. It is capable of converting all offline mailbox items without compromising on their integrity. What more? Any user can check the efficiency of this software by downloading its free trial version.

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