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Migrate an Offline File (.ost) to outlook (.pst) with Ease

Published on 19 July 17

MS Outlook uses Offline Storage Table (OST) file when the cached mode is enabled from an Outlook account that will associate it with Exchange Server. This file allows user to work in offline mode without connection to the Exchange Server. Any alterations made in the mailbox during this mode will be synchronized to Server when there is connection. However, due to several issues related to the OST file, most of the users wish to migrate OST to PST file. The article will be discussing methods on how user can carry out the migration from an offline(.ost) file to Outlook(.pst )format.

Issues related to OST files

The main reason why most of the users of Outlook need to migrate their Exchange OST mailboxes to PST files are the issues of OST file. Some of the issues that could make the OST file inaccessible or corrupted are as follows:

  • Exceeding OST Size Limit Issue : Every Outlook versions comes with variant size limits supported while dealing with the OST file. In earlier version of Outlook, only 2GB storage was allowed, which was later increased up to 20 GB in Outlook 2007. Now in the recent versions, limit has been increased to 50 GB in Outlook 2010/2013. However, the maximum default size limit defined is 20 GB, which is the reason why the performance of Outlook slows down when it exceeds or reaches this size limit.
  • OST file in Orphaned State : Every single OST file is associated with a particular Exchange Mailbox and any changes made in offline mode is automatically synchronized to MS Exchange Server. When the Exchange Mailbox either is dismounted or deleted from the Exchange server, the OST file will be inaccessible that could lead to orphaned state.
  • Interrupted Synchronization : This problem arises if there is any kind of disturbances while the OST file is being synchronized with the MS Exchange Server. Since the OST file is in encrypted form, decryption key of the Outlook profile needs to be matched with the one present in Exchange Server. If it does not match, synchronization issue will be encountered that can make the OST file inaccessible.
  • OST Bound to MAPI Profile : As each OST file is bound to a specific MAPI profile, contents in the OST file can only be accessed when the user login using the authorized credentials of the same profile, that was used to create the file. In case of authentication failure, client will restrict user from accessing the Exchange OST file and data stored in it. The OST file cannot be accessed even after copying it in any other Outlook account like PST.
  • Corruption issue in OST : The OST can be corrupt when there is an unexpected power shutdown during synchronization, improper handling of OST file, virus attack, destruction of hard drive/local storage where the OST file was stored, etc. OST files in corrupted state can make the file inaccessible and loss of data.

Need of OST to PST Migration

  1. Avoid Data Loss: The issues in OST file like virus intrusion, power shutdown, server failure, etc. makes OST file inaccessible resulting to loss of data. Therefore, in order to avoid loss of data, a copy of OST file can be saved in PST file format.

  2. Access any OST in Outlook: Conversion of Exchange OST to PST makes it accessible in any Outlook account. As OST file cannot be just copied and used while PST can be copied in Outlook to access its contents.

  3. Backup of OST File: Migration of OST to PST file helps in creating backup of the OST data in PST format to keep the data secured and protected from wrong hands.

  4. Absence of Exchange Server: Employees switching from one organization to another organization cannot access the OST file contents if there is no Exchange Server Connection.

  5. Exchange Server Crash: Crash in Exchange Server makes the mailbox inaccessible, which is why OST file needs to be converted to PST file in order to access the data.

Some Points to be considered before Conversion

There are some points that user needs to keep in their mind before the conversion of OST to PST file is carry out. They are stated below:

  • It is necessary to have MS Outlook installed on a local system that is configured with Exchange Server. Additionally, the presence of valid connection is needed to migrate from the OST to PST file.
  • The Export process needs to be performed on the same local system where OST files were originally created.
  • A new Outlook data file in PST format needs to be created where all the desired items from mailbox can be exported or moved.

Methods to migrate OST to PST

  1. Using Import and Export Feature

Since MS Outlook does not provide any direct utility for the conversion of OST to PST file, we can use a workaround that will help users to export the data in OST file to PST file by following the steps below:

  • Click on Start > All Programs > MS Outlook
  • Select File Tab on the uppermost menu bar and click Open Import
  • The Import and Export Wizard will be launched, where user will select ‘export to a File’ option and click on Next
  • Choose Outlook Data file (PST) among the available file formats given in the list and click on Next to proceed
  • Browse the mailbox folder from where the data needs to be export from and select Next
  • Define the destination location where the new PST file need to be saved and click on Finish
  • Ensure that new Outlook PST file is present in the location that has been defined by the user.
The drawbacks of using this approach is usage of the import and export feature needs user to have technical knowledge that most of the user lacks. Another point is it also needs the connection of MS Exchange Server in order to carry out the migration process.

2. Drag and Drop Items to new PST

The second approach involves user to create a new PST file in MS Outlook. We will select the desired mailbox items from OST, drag and drop them to the newly created PST file.

However, this method has weaknesses too that is user can migrate only the individual items from the OST file to the new PST file. In addition to this, folder structure and the default folders like inbox, drafts, contacts, etc. cannot be migrated. Instead, user can create another new PST file and reorganize all data accordingly. This approach is not much effective as it involves drag and drop of the individual items that can consume lots of unnecessary time.

Both the above methods do not support conversion of corrupted OST to PST files. However, MS Outlook provides an Inbuilt Repair Utility for the repair of damaged or corrupt OST and PST files. Earlier, scanost.exe was used to repair the OST files, which was later replaced by scanpst.exe in MS Outlook 2010 for repairing both OST and PST files. Though using this repair utility makes the corrupted OST file a healthy one, it cannot recover the complete data and takes unnecessary time. This utility will delete the corrupt part of the OST file making the file healthy and recovering only the uncorrupted part.

After considering all the methods that has some or other drawbacks, users can go for one third-party solution that overcomes all the drawbacks of the above manual methods i.e., OST Recovery. It is an effective tool for the conversion of any OST file to PST and other file formats without any data loss. The software has been equipped with such feature that deals with any type of OST files regardless of their states from healthy to highly corrupted files. It ensures that the original formatting or the Meta-properties of all the data items in OST file is preserved after it has been converted to PST file. The tool supports selective export of the mailbox items in OST file and does not impose any size limitation on OST file. The best feature of the tool is that it extracts & recovers permanently deleted messages from OST file and presence of MS Outlook is not necessary for the migration.


The article has been aimed to guide users migrate their Exchange OST file to Outlook PST file in order to overcome the issues related to OST file. It also describes multiple issues explained in depth that could lead to conversion of OST to PST files. The need of conversion has been stated along with the points to be considered before carrying out the migration process. Several approaches have been explained that user can use to convert their OST file contents in PST file format. Users can opt any of the conversion methods as per their requirements. In the end, the article has come up with reliable software that is used to convert the OST to PST files maintaining the data integrity.

This blog is listed under Development & Implementations and Data & Information Management Community

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  1. 22 August 20

    SysOZ OST to PST Converter Software that secure for repairing corrupted or damaged OST file and recover OST file to PST file. Using application is very easy, just follow the easy steps of installing and get the secure process for repairing and recovering exchange Outlook OST file emails, contacts, calendars, task, notes, inbox items, outbox items, journals and appointments. Read More:

  2. 16 July 18

    OST to PST Converter tool is an advanced application which works on all Windows Operating Systems. The main characteristics of this tool are that it's effectively converted OST file data to PST, MSG, EML, RTF and HTML format. The tool also repairs corrupted or damaged OST file and save the recover data at user defined location. To get more info at:-

  3. 07 September 17

    OST to PST Converter software is best solution for converting and recovering database from Exchange Server OST file format to PST file format. Conversion will help you to transfer all items like emails, contacts, to do list, journals, tasks, attachments and calendars etc. Today I am suggesting you a tool that will not only convert OST to PST but also helps you to transfer your database from OST file to PST, EML, DBX, MSG and MBOX file format. Source link:-

  4. 24 July 17

    Specifically programmed to provide instant results, OST to PST Converter extracts all the unreadable items in the accessible and readable offline storage files. As the name suggests, it actually extracts the inaccessible and orphaned OST and recovers all the mailbox items into PST file format. With its innovative GUI, the tool is user-friendly and makes the conversion process a lot smoother.Download free trial version to get the preview of your convertible emails -

  5. 21 July 17

    Migrate mailbox data from Offline storage table (OST file) to personal storage table (PST file), with the help of a secure an reliable third party solution, Exchange OST to PST. The software is also capable to perform easy an error free migration of OST files to EML, MSG, RTF, TXT, PDF, HTML, MHTML, MBOX and DBX. For more information, visit-

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