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How to convert an OST file to a PST file

OST to PST file converter

Outlook Recovery Kit

Outlook Recovery Kit helps to convert OST to PST files

How to convert an OST to a PST file

A step-by-step manual for the conversion of Exchange Server OST files to Microsoft Outlook PST files. This instruction helps to convert OST to PST files with all messages, contacts, appointments, tasks, notes, journals, calendars and so on:

  1. Download Outlook Recovery Kit here
  2. Install Outlook Recovery Kit in Windows
  3. Start Outlook Recovery Kit
  4. Select an OST file on the first page of the program
  5. Select the Converter mode mode
  6. View the content of the OST file
  7. Select a folder for saving converted data
  8. Select the Save as PST file mode
  9. Click Save
OST to PST converter

Microsoft Outlook OST to PST converter

OST-to-PST conversion is an added feature of Outlook Recovery Kit. Outlook Recovery Kit can convert .ost files from any version of Microsoft Outlook or any version of Microsoft Exchange Server into the .pst file format without Exchange Server or Windows Domain Controller.

Features of OST-to-PST conversion software:

Outlook Recovery Kit helps to import OST files in Microsoft Outlook in a few easy steps:

  • Start Outlook Recovery Kit
  • Select or find on the disc OST file on the first page of Outlook Recovery Kit
  • Select the mode Conversion
  • Select folder for saving PST file with data
  • Start Microsoft Outlook
  • Delete the OST file from system settings. Menu: File | Account setting. Tab menu Data file
  • Open saved PST file in Outlook through menu: File | Open&Export | Open Outlook Data File

Import of OST files in Outlook

Outlook Recovery Kit is OST-to-PST converter and an Outlook OST recovery tool at once.


  • Windows 98/Me/2000/XP/Vista/7/8/10/11 or Windows Server 2003/2008/2012/2016 and above
  • Microsoft Outlook 98, Microsoft Outlook 2000, Microsoft Outlook 2002, Microsoft Outlook 2003, Microsoft Outlook 2007, Microsoft Outlook 2010, Microsoft Outlook 2013, Microsoft Outlook 2016, Microsoft Outlook 2019, Microsoft Outlook 2021 (Microsoft 365) must be installed on the user’s computer at the time of conversion (excluding Outlook for Office 365, Outlook for iOS and Outlook for MacOS).

This product does not export contact groups.


This OST-to-PST converter is an easy-to-use tool that operates like a wizard. With it, you can convert an .ost file to the .pst file format in a few simple steps. No special know-how is needed in order to use the Outlook Recovery Kit OST-to-PST converter.

Microsoft doesn't currently offer a special Outlook OST-to-PST converter. All OST2PST converters have been designed by ISVs. Outlook Recovery Kit, however, has a demo mode that lets you convert five objects per folder.


Outlook Recovery Kit can read *.ost files any versions of Microsoft Exchange Server, any version of Microsoft Outlook (32- or 64-bit, ANSI or UNICODE). Software can read and convert *.ost files with any size of file.


The size of the converted .pst file shows the actual size of information stored in the ost file. If you do not make archives and do not start Cleanup Tool regularly for the original Offline Storage Folders, then the .ost file size is only growing. As a result, only 5-10% of the file can be used for a real user's data.


For the use of OST-to-PST conversion on a computer running Microsoft Outlook, the .pst file version will be the same as that installed in Microsoft Outlook. If the computer has Microsoft Outlook 2007 or higher installed, the size of the resulting .pst file can exceed 2Gb. If you use MS Outlook 98-2003, the size of the resulting file will be limited to 2Gb. In this case, Outlook Recovery Kit will create several .pst files in which to store all the data from the source .ost file.


Outlook Recovery Kit exports messages, contacts, appointments and other data from *.ost files as MSG files. The software converts and saves all data from .ost files to the .msg file format. Later, the user can drag and drop or import the saved *.msg files in any of the popular client software programs, including Lotus Notes, Microsoft Live, The Bat, Eudora, Incredimail, Mozilla Thunderbird, etc.


Microsoft Outlook has no function with which to import data from *.ost files. To open an *.ost file in Outlook, the Exchange Server and Windows Domain Controller must be working and available for user authentication in both of the respective services. Only after that is it possible to transfer the contents of an .ost file that is open in Outlook to a .pst file that is also open in Outlook.

If the Exchange Server or Windows Domain Controller isn't accessible or doesn't work, or if the user can't be authenticated, access to the data will be denied and Outlook won't open the .ost file.


The original .ost file must be converted to a pst file using Outlook Recovery Kit and then opened in Outlook. Conversion from OST to PST using Outlook Recovery Kit doesn't require the availability of Exchange Server or Windows Domain Controller.


Our engineers have analyzed the content of OST (source) and PST (destination) files. The analysis revealed the types of data that are not carried over to the PST file after OST file conversion:

  1. old versions of messages, contacts, files and other objects
  2. removed objects
  3. blocks of data from earlier versions of messages, contacts, files and other objects. It is impossible to use these blocks to fully recreate the original object, which is why they can be treated as junk.

In other words, when you remove or modify a message, contact, reminder or meeting, the object is only marked as removed, but is not removed physically and remains in the OST file. The new version of the object is written to a newly allocated space, but the old version remains in the OST file as well.

If Outlook is in active use, the size of the OST file can grow quite significantly, while the actual size of data in the file remains the same.

In order to optimize disk space consumption and remove old elements, you need to configure the AutoArchive feature in Microsoft Outlook.


  • search for and reading of old versions of documents is used by attackers for stealing users’ confidential information;
  • search for and reading of deleted and old versions of documents is used by police authorities to collect compromising information (Forensic Mode);
  • Outlook Recovery Kit enables the user to search for data deleted from an OST/PST file and save it to the disk.


Repairing mailboxes after the corruption of the Exchange Server database file. If the Exchange Server database file gets damaged, the server will still have *.edb files with users' emails. There will also be .ost files on users' computers containing the personal data of each user.

OST files can be quickly and easily converted to PST files using Outlook Recovery Kit. You can try recovering .edb files using Exchange Server Recovery Kit. This tool converts individual mailboxes to .pst files. We recommend trying both recovery methods to recover as much data as possible.


Since the internal folder structure in the .ost file is slightly different from the .pst file, to search for folders merely open all the folders of the 1st and 2nd level in the .PST file in Microsoft Outlook. Usually, user folders are at the second level.

Select or find on the disc OST file on the first page of Outlook Recovery Kit:

Please select a mode for program use:

  • Converter Mode – use it for export data from OST to PST files.

Select folder for saving PST file with data:

Selecting the source *.pst file you want to repair

Select work Mode

Reading (detecting and recovering) data from the selected *.pst file

Specifying the path where to save the recovered data

Selecting the method of saving the recovered data

Saving the data to the disk