DataNumen Outlook Repair is the most effective way to fix corrupt Outlook PST files:

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Now, let’s discuss why the PST files will get corrupted. There are so many reasons that will let your Outlook PST file corrupted or damaged. We classify them into two categories, i.e., hardware reasons and software reasons.

Hardware Reasons:

Whenever your hardware fails in storing or transferring the data of your MS Outlook PST files, the PST files will likely get corrupted. There are mainly three types:

  • Data Storage Device Failure. For example, if your hard drive has some bad sectors and your Outlook PST file is stored on these sectors. Then maybe you can only read part of the PST data file. Or the data you read are incorrect and full of errors.
  • Faulty Networking Device. For example, the Outlook PST file resides on the network server, and you try to access it from a client computer, via network links. If the network interface cards, cables, routers, hubs and any other devices constituting the network links have problems, then the remote access of the PST file may make it corrupted.
  • Power Failure. If a power failure happens when you are accessing the PST files, that may leave your damaged PST files.
  • Misoperations. For example, if you unplug an external hard drive when copying a PST file to it, then the PST file will get corrupted.

There are many techniques to prevent or minimize the Outlook PST file corruption due to hardware problems, for example, UPS can minimize the power failure problems, and using reliable hardware devices can also reduce the chances of data corruption.

Software Reasons:

Also many Outlook PST file corruptions occur due to software related issues.

  • Incorrect File System Recovery. You may find it is unbelievable that a file system recovery may cause PST file corruptions. But in fact, sometimes when your file system is broken, and you try to hire a data recovery tool or expert to recover the PST files on it, the files recovered may still be corrupt, because:
    • Due to the file system disaster, some parts of the original PST file are lost permanently, or overwritten by garbage data, which makes the final salvaged PST file incomplete or contain incorrect data.
    • The recovery tool or expert doesn’t have enough expertise that it/he may collect some garbage data and save them as a file with .PST extension. As these so-called .PST files don’t contain any valid data of the Outlook files, they are totally useless.
    • The recovery tool or expert has collected the correct data blocks for the PST file, but has not combined them in a correct order, which also makes the final salvaged PST file unusable.

    Therefore, when a file system disaster occurs, you should find a good data recovery tool/expert to recover your PST files. A bad tool/expert will make the situation worse instead of better.

  • Virus or Other Malicious Software. Many viruses will infect and damage the Outlook PST files or make the mailbox items inaccessible. It is highly recommended to install quality anti-virus software for your Outlook email system.
  • Terminate Outlook Abnormally. In normal situation, you should quit Outlook gracefully by saving all your changes to the PST file and then clicking “Exit” or “Close” menu item. However, if Outlook is shut down abnormally when you are opening and accessing the PST file, then the PST file is prone to corrupted or damaged. This can happen if power failure mentioned above occurs, or if Outlook is busying in doing something and you terminate it by click “End Task” in Windows Task Manager, or if you turn off the computer without quitting Outlook and Windows normally.
  • Abnormal system shutdown. This is similar to terminating Outlook abnormally. When Outlook is still open and your system shutdowns abnormally, the PST file will get corrupted easily.
  • Deficiencies in Outlook data file format. PST and OST are the main Outlook data file formats. Both of them are not robust and well-designed for reliable and long-term storage of large volumes of data. So file corruptions are very common and frequent.
  • Deficiencies in Outlook application. Every program has deficiencies, so does Outlook. Some deficiencies come from the short sights of the designers. They can usually be expected but cannot be solved simply by fixes or patches. For example, in the early days, the Microsoft designers don’t believe there will be bulk of data in PST files, so the maximum size of PST file for Outlook 97 to 2002 is 2GB by design. But nowadays, the communications and personal information grow so quickly that the PST file increases dramatically. When the PST file approaches or goes beyond 2GB, it will get corrupted. While the other deficiencies result from the carelessness of the programmers. In general, they cannot be expected but once found, can be solved by small fixes or patches. For example, when MS Outlook encounters an unexpected error, it will say “Microsoft Outlook has encountered a problem and needs to close. We are sorry for the inconvenience.” and terminate abnormally, which is very likely to make the PST file corrupted.

Symptoms of Corrupt PST Files:

Below are some common symptoms when PST data files are corrupt:

We also collect a more complete list so that you can match your case there.

Fix Corrupt PST Files:

  1. You can use our award-winning product DataNumen Outlook Repair to recover your corrupt PST files.
  2. You can use DataNumen Outlook Drive Recovery to scan the drive or disk where you have stored your Outlook PST files in the past, and then recover data from it.
  3. You can use scanpst.exe (Inbox Repair Tool) to scan and recover your corrupt PST files.


How many disk spaces are required for the new PST file?

Normally if the original corrupt PST file size is S, then you’d better prepare at least 1.1 * S free disk spaces for it.

How to find the Outlook PST file to be repaired?

Method 1: You can click the search button in our Outlook PST repair tool to search for the PST files on the local computer. Then select the one you want to repair.

Method 2: You can search for the PST files in Windows.

Method 3: You can do as follows:

  1. Open Outlook.
  2. Click File > Account Settings. In the drop-down list, click Account Settings.
  3. In the pop-up Account settings dialog, click Data Files tab to see the PST file path.

Do I need to make a backup of the source PST file before the repair process?

No. Our recovery software will only read data from the source PST file. It will NEVER write into it. So the repair process will not make any changes on the source PST file. And you do NOT need to make a backup of it.

What is a PST file?

PST is the Personal Storage Table file format, also called Outlook Personal Folders file format. It is a kind of Outlook data file. It stores Outlook emails, folders, posts, calendars, appointments, meeting requests, contacts, distribution lists, tasks, task requests, journals, and notes.

Our PST repair tool is mainly designed to repair corrupt PST files.

What is an OST file? Can your tool repair it?

OST is the Offline Storage Table file format. It is also a kind of Outlook data files. Outlook uses it to cache all mailbox items in Cached Exchange Mode, when working with Exchange Server and other types of accounts.

Our tool can also repair corrupt OST file and convert it to PST file.

Are there any free ways to repair corrupt PST files?

Yes, Outlook has a built-in tool called scanpst.exe, which works in a few cases when the PST (Personal Folders) file only has minor corruptions. You can use the following table to find it:

Install Type 32bit Windows 64bit Windows
Outlook 2016/2019(32bit) Normal C:\Program Files\Microsoft Office\Office16 C:\Program Files (x86)\Microsoft Office\Office16
Outlook 2016/2019(64bit) Normal N/A C:\Program Files\Microsoft Office\Office16
Outlook 2016/2019(32bit) Click to Run C:\Program Files\Microsoft Office\root\Office16 C:\Program Files (x86)\Microsoft Office\root\Office16
Outlook 2016/2019(64bit) Click to Run N/A C:\Program Files\Microsoft Office\root\Office16

For earlier versions of Outlook, you can replace Office16 with the corresponding folder name, as below:

Outlook Version Folder Name
Outlook 2013 Office15
Outlook 2010 Office14
Outlook 2007 Office12
Outlook 2003 Office11

After you find scanpst.exe, please do as follows:

  1. Double-click to run it.
  2. Click the Browse button to select the PST file to be repaired.
  3. Click the Start button to repair the corrupt PST file.

However, for most of the cases, scanpst.exe will crash or not work. As a reference, we have collected a complete list of the symptoms that scanpst.exe fails. In such cases, you’d better use our recovery software to repair your file.

Which versions of Windows are supported by your tool?

Our file recovery tool supports Windows XP/Vista/7/8/8.1/10/11 and Windows Server 2003/2008/2012/2016/2019.

How many disk spaces are required to install your tool?

We recommend you keep at least 50MB on your hard drive to install our tool.

Is Microsoft Outlook required to run your tool?

Yes, you need to have Microsoft Outlook installed on your local computer so that our tool can run and repair the corrupt PST files.

Do I need to close Microsoft Outlook when running your tool?

Yes, we recommend you to do so. Before starting our PST repair tool to repair damaged PST files, please close all other applications, including Microsoft Outlook application.

Which versions of Outlook are supported?

Our tool supports MS Outlook 97 to 2019 and Outlook for Office 365.

How long does it take to repair a corrupt PST file?

The time of the repair process depends on several factors, including the PST file size, the complexity of the PST file, the computer configuration, etc. Normally it requires several hours to repair a 10GB PST file on a modern computer.

Can you recover deleted emails and folders?

Yes, our tool can recover permanently deleted emails and folders from the PST files. We enable these features by default. You can also change the settings by:

  1. Start our recovery software.
  2. Click the Options tab.
  3. Click the Advanced Options tab in the left panel.
  4. In the Recover Deleted Items group, you can enable or disable the Recover deleted folders and Recover deleted messages options.

Why do you save the output file in PST format?

Outlook can open Outlook PST files directly so that you can access its contents easily. Also, Exchange Server can also import PST file data easily.

What is the structure of the new PST file?

The new PST file will have the same folder structure as the original corrupt PST data file. Our tool will recover the folders, then put the emails to their original folders.

Moreover, there will be some lost & found items. We will put them into some lost and found folders called Recovered_Group#, where # is a sequence number starting from 1.

Are there any size limits on the PST files? What are the solutions?

Yes, below are the size limits for different versions of Outlook, together with the corresponding solutions:

Outlook Version Size Limit(GB) Hard Limit Solution
Outlook 97 – 2002 2GB Yes This limit is due to the design deficiency of the old PST format. So the only solution is to convert the old PST format to the new format.
Outlook 2003 – 2007 20GB No This limit is set in the registry, below are the solutions:

  1. Change the registry values.
  2. Split large PST files to smaller ones.
Outlook 2010+ 50GB No Same as Outlook 2003 – 2007

How to repair a corrupt PST file with your tool?

It is very simple, as follows:

  1. Start our recovery software.
  2. Click the Browse button to browse and select the corrupt PST file to be repaired.
  3. Click the Start Repair button to start the repair process.

You can also see a more detailed step-by-step guide by visiting the DataNumen Outlook Repair homepage, then click “How to Recover” tab. You can also find a video tutorial there.

Can you output recovered emails as .eml files?

Sorry but our file recovery tool does not support such a feature directly. But you still can do so manually, as below:

  1. Repair the corrupt PST file and get a fixed PST file.
  2. Open the fixed PST file in Outlook.
  3. Export the wanted emails to .msg format.
  4. Use MFCMAPI to convert the .msg file to .eml format.

You can get more detailed instructions by visiting the DataNumen Exchange Recovery homepage, then clicking “More Information”, then clicking the “FAQ” tab.

Can you output recovered emails as .HTML files?

Sorry but our Outlook PST repair tool does not provide such a function directly. But you can still do so manually, as below:

  1. Repair corrupt PST file and output the recovered PST file.
  2. Open the recovered PST file in Outlook.
  3. Export the wanted emails to .HTML format.

I cannot find wanted emails in the recovered PST file. What can I do next?

First of all, you’d better find your emails carefully in the recovered PST(Personal Storage Table) file. There are 3 ways you should try:

  1. Find emails in their original folders. For example, if your wanted emails are in the Inbox folder, then you should check Inbox in the recovered PST file and look for the wanted emails.
  2. Find emails in the lost and found folders. Folders like Recovered_Group### are lost and found folders. Sometimes, your wanted emails are not normal items, but lost and found items. So you can try to find them in the lost and found folders accordingly.
  3. Search the whole PST file for the wanted emails, with their subjects or other information. Sometimes, due to file corruption, the recovered emails are not put back to their original locations or the lost and found folders. In such a case, you can try to search the whole PST file.