Microsoft Outlook Data File Repair Research – A Deep Dive

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At Remo Research Lab, we studied how Outlook data file corruption occurs, tested Scanpst in various cases, and also explored how Remo Repair Outlook handles it.

Read on to know valuable insights about Outlook data File repair.

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Outlook data file corruption is a common and critical issue faced by Microsoft Outlook Users, which can be very distressing.  Microsoft provides a tool to repair the corruption of PST files, popularly called SCANPST. This research will take you on a technical deep dive into how scanpst.exe performs on different corrupted PST cases.

Knowing Scanpst.exe:

Scanpst.exe, commonly known as "Inbox Repair Tool," is an integral part of the Microsoft Outlook software suite. It's a simple and easy-to-use tool for fixing issues with data files. It works by checking, identifying, and trying to repair any problems or inconsistencies it finds in the PST and OST files.

However, several limitations can affect its effectiveness in specific scenarios.

  • Incomplete Data Recovery: scanpst.exe exhibits limitations in achieving comprehensive data recovery. It primarily focuses on the structural aspects of the PST or OST file and may not fully restore data items like emails, contacts, or attachments.
  • Handling Large File Sizes: scanpst.exe demonstrates suboptimal performance with large or oversized data files. Repairing such extensive PST files may result in prolonged processing times, and complete resolution may not be guaranteed.
  • Complex Corruption Challenges: When confronted with severe or intricate data file corruption, scanpst.exe may not effectively rectify all issues. Multiple iterations of the tool may be required to achieve a thorough repair.
  • Compatibility Concerns: The utility is primarily tailored for specific Outlook versions, which can lead to compatibility concerns when handling files originating from different Outlook versions or other sources.
  • Data Integrity Risk: During repair attempts, scanpst.exe may inadvertently modify or delete certain data elements, posing a potential risk of unintended data loss. Users should be more cautious when using the tool.

Performance of scanpst.exe on various case scenarios:

We put scanpst.exe to test to understand how it performs in different scenarios of PST corruption.

Scenario 1: We will start with the basic deletion of emails permanently and see how the tools perform.

Selected three emails out of eight from a folder in the inbox and deleted them permanently.

Opened the scanpst.exe from the location C:\Program Files\Microsoft Office\root\Office16 selected the PST file, and started the scan

select the PST file and scan

It scans the PST file recognizes errors and gives the option to take backup before repairing the file and select backup file location. By default, the backup option will be selected, and the location will be the same as the folder from which the PST file is chosen to repair; it can be editable.

select a backup location

Upon successful completion of the repair, I opened the PST file in Outlook to see if it had recovered the deleted email. Scanpst.exe couldn’t recover the deleted emails.

Once an email is deleted in Outlook, it typically moves to the Deleted Items folder (or the Trash folder). Users can permanently delete the items from there, making them unrecoverable through normal Outlook functions. Scanpst.exe cannot retrieve items that the user has intentionally and permanently deleted.

While attempting to repair a damaged PST or OST file, scanpst.exe could replace certain file sections to address structural problems. If an email was deleted but still existed in the data file, running scanpst.exe may further decrease the chances of recovery, as it could potentially overwrite the space where the deleted email resided.

For this reason, we have taken a copy of the PST file before attempting the repair of the file with scanpst.exe

One of the most popular tools we have developed at Remo Software is Remo Repair Outlook (PST), so we tested it on the same case. Selected the copy of the PST file with deleted emails and initiated the scan, Remo Repair Outlook (PST) is able to recover the deleted emails and list all the eight emails from the inbox folder.

recovered emails by the Remo Repair Outlook

When analyzing the internal PST/OST file, we collect data blocks that store emails, contacts, tasks, attachments, calendar items, and more. Each data block is a well-organized data structure with a B-Tree, tables, and indexes. After validating and collecting each data block, we create a new .pst file and copy the collected data within it.

Remo Repair Outlook creates a new PST file instead of altering the original one. On the other hand, scanpst.exe attempts to repair a corrupted PST or OST file by overwriting some parts to fix structural issues. This process may further decrease the chances of recovering deleted emails.

Scenario 2: PST Header Corruption

The header of a PST file is crucial as it contains critical information about the file's structure, including folder hierarchy, data file properties, and pointers to data elements. However, if the header gets corrupted due to sudden Outlook crashes, conflicts with other software, or hardware issues, it can cause difficulties in accessing or using the PST file. To address this, we will manually corrupt the header of the PST file and attempt to repair it.

header of a healthy file

The above image shows the header of the healthy PST file. We have corrupted 0x80 bytes in the header from offset 0x80 to offset 0xFF, which is as shown in the image below.

header of a corrupt PST file

When the header of the PST file is corrupted, on launch, Outlook prompts a message saying, “Something is wrong with one of your data files, and Outlook needs to close. Outlook might be able to fix your file. Click OK to run the Inbox Repair Tool.”

inbox repair tool

Clicked on OK to initiate the repair process, scanpst.exe launched and started the repair process by clicking the Start button. While analyzing the PST file, scanpst.exe crashes before the process is complete.

Watch scanpst.exe behavior while repairing the PST file with header corruption.

Now, let’s run Remo Repair Outlook (PST) on the same PST file with header corruption.
Remo Repair Outlook (PST) successfully repaired the PST file and was able to list the contents.

repaired PST file listed in Remo Repair Outlook

Understanding the header of a .PST file is crucial for our analysis. This component provides critical information about the file's organization and structure. It holds valuable insights into various data structures used in the file, including B-Trees, tables, indexes, and data blocks.

In addition, it contains vital flags and configuration settings that control how the PST file is read, written, and maintained, such as encryption or compression preferences. Moreover, the header references the root folder entry, the starting point for navigating the entire hierarchy of folders and items within the PST file.

Additionally, it includes details about the offset and size of the data section, aiding in locating and retrieving the actual email messages, attachments, and other data contained within the file.

Before proceeding with the data collection process, one crucial step is validating each data block. This is a fundamental aspect of our approach to ensuring the integrity and reliability of the stored data. The validation process thoroughly examines every data block within the PST or OST file. We carefully examine these data blocks to verify their accuracy and completeness, forming a comprehensive data representation.

By validating each data block, we aim to identify and address any issues that may have arisen due to various factors, such as file corruption, software errors, or hardware issues. Data blocks not meeting our validation criteria may be flagged for further investigation or repair.

A new .pst file is created to store the data securely. Subsequently, we transfer all the validated data blocks into this newly created file, preserving and meticulously organizing the essential information for easy access and usability.

Scenario 3: File structure corruption

File structure corruption can occur due to various factors such as sudden power loss, system crashes, software glitches, virus infection, abrupt outlook termination, etc. When the structure of a PST file becomes corrupted, it can lead to data loss and issues with accessing email, contacts, calendars, and other Outlook data. We have corrupted the file structure of a PST file by filling in junk values and zeros at multiple places.

PST file structure corruption

If we try to open Outlook with a PST file that has file structure corruption, it will display a message that says, "Something is wrong with one of your data files, and Outlook needs to close. Outlook might be able to fix your file. Click OK to run the Inbox Repair Tool."

When I clicked OK to start the repair process, scanpst.exe was activated, and upon clicking the "Start" button, it began to repair the file. Unfortunately, scanpst.exe unexpectedly stopped working before completing the analysis of the PST file.

Let's put Remo Repair for Outlook PST to test to repair the PST file with file structure corruption.
In our analysis of PST and OST files, we focus on collecting the vital data blocks while omitting any empty or unnecessary sections. These files contain data blocks that store essential information, including emails, contacts, tasks, attachments, calendar items, and more. The data blocks are structured efficiently, similar to organizing data in a well-structured database.

Before we gather these data blocks, we thoroughly validate each one to ensure it's accurate and complete. The final step involves creating a new .pst file, which acts as a clean container to store the data securely.

Then, we transfer all the validated data blocks into this new file. This ensures that the emails, contacts, and other valuable information are preserved, organized, and ready to access and use as needed.

Remo Repair Outlook (PST) successfully repaired the PST file with file structure corruption.

successfully repaired PST file by Remo Repair Outlook

In short, SCANPST is a free and easily accessible option, but be cautious—it changes your existing PST file. This alteration can be a major issue, so it's advised to explore alternative solutions to prevent unintentional data modifications.

VITAL ADVISORY (PAY CLOSE ATTENTION): Always safeguard a duplicate of the original PST File before initiating SCANPST.EXE. It's imperative to avoid a scenario where the issue persists, and the original file undergoes modifications during repair, rendering it still unusable. Protect your data – keep a backup!


As showcased earlier, Remo Repair for Outlook PST stands out as a more secure option for end users, offering increased stability compared to scanpst.exe, especially when dealing with intricate cases of header corruption and file structure issues. It excels in recovering deleted emails from the PST without impacting the integrity of the original file.

It’s a shot in the arm for us at Remo Research Labs to deep dive into such case scenarios to make sure what we develop is going to help the most users in distressing situations. Consider Remo Repair for Outlook PST as a superior alternative for your recovery needs.

About the Author: Praneeth

Praneeth Anand is a skilled product manager and research analyst with a strong background in the tech industry. He is currently employed at Remo Software, a leading provider of data recovery solutions. Praneeth's expertise in data recovery software’s, market research, and strong connect with storage devices has been instrumental in Remo Software's success. He is…