Reasons for Outlook PST File Corruption

Although Outlook is a robust messaging and calendaring application that dominates the desktop email client market with millions of users across the globe, it suffers from a major flaw related to Outlook data files, such as PST file corruption.  

The majority of issues with Outlook are encountered due to problems with the Outlook PST file that stores a copy of mailbox items, such as emails, contacts, attachments, calendar items, notes, tasks, etc., on the local drive.

When this Outlook PST data file is damaged or inaccessible, it can lead to Outlook errors and prevent users from accessing their accounts or receiving new emails. Not to mention, PST corruption may also lead to data loss.

In this article, you will learn about the various reasons behind PST file corruption and tips to prevent them from damaging your PST file. We have also shared methods to repair a corrupt or damaged PST file and recover your mailbox data.

Causes for Outlook PST File Corruption

Usually, Outlook PST file damage or corruption is caused by hardware and software-related issues. Below we have discussed these reasons in detail to help you understand the causes and prevent them to avoid PST file corruption.

Large PST File Size or Oversizing

In earlier Outlook versions, such as Outlook 2003 and 2007, the recommended ANSI PST file size limit is 2GB. However, Outlook 2010 and later uses a UNICODE PST file with a recommended file size limit of 20GB. When the PST file reaches or exceeds this recommended limit, Outlook performance goes down. As a result, users notice a delay in accessing their mail items and sending or receiving emails.

All these are the early sign of a problem with the PST file. As PST file grows larger after exceeding the limit, inconsistencies may develop, leading to errors and ultimately causing PST file corruption.

Tip: To prevent PST file corruption due to oversizing, use the Archive option in Outlook and regularly clean Deleted Items and Spam folders. For detail, refer to this guide on reducing the PST file size. 

Outlook or System Crash

Windows or Outlook may crash anytime due to hardware failure, operating system issues, or problems/conflicts with software. If the system or Outlook crashes while working, it can damage the PST file and lead to data loss. In some cases, if the crash occurred due to a severe issue, you may not be able to reboot the system and lose mail items permanently.

Tip: To avoid such situations, use a system with decent hardware configuration and keep the system optimized with updated software. Never install a beta version of the Operating System or any other software you often use to avoid such incidents.  

Abrupt Shutdown

Like a system crash, an abrupt shutdown due to power failure or force shut down due to system freeze while Outlook is running can have severe consequences on the PST file stored on your system. Such events sometimes can cause irreparable damage to the PST file leading to significant data loss. 

Tip: Abrupt shutdowns are usually caused by power failure. To avoid such situations, use an uninterrupted power supply or UPS. If using a laptop, keep an eye on battery health and keep the charger connected if the battery is faulty or does not provide enough backup. If the battery is defective, replace it immediately.

Force Close Outlook

Outlook may freeze or stop responding if your system hardware is not capable or there’s an issue in retrieving some mail items. There could be an urge to force close the Outlook immediately using the Task Manager and restart to resume whatever you were doing. However, force closing Outlook can also cause PST file corruption.

Tip: The Outlook froze because it could not complete a task, such as updating or processing the PST file and was stuck responding to your commands. In such a situation, you should wait for a while for Outlook to start responding. However, if it still doesn’t respond, you may go ahead and force close it and then restart. In a nutshell, always wait for the program to respond before force closing to avoid PST file corruption.

Incompatible or Faulty Add-In

Incompatible or faulty add-ins can cause a series of issues and problems in Outlook, such as errors in sending or receiving emails. Slow Outlook performance, delay in search results or damage the PST file.

Tip: You should never install any add-in from unknown or untrusted sources. Always use Microsoft Store to install any add-in in your Outlook or other Office application.  

Storage Drive Errors or Damage

Errors in storage media, such as file system issues or bad sectors, can damage the PST file header or some part stored on the sector that has gone bad. Low available storage can also impact the PST file and lead to Outlook errors. Your drive could also crash or stop responding, which can cause system freeze and crashes leading to damaged or corrupt PST files.

Tip: Keep an eye on the disk health using a SMART drive monitoring tool. If the drive is displayed as unhealthy, stop using it to avoid data corruption and system crashes leading to data loss.

Virus or Malware intrusion

Virus and malware intrusion may occur from opening a malicious email, link, or attachment that the user has received in Outlook. A virus may also enter if you often use a flash drive to transfer data between the devices without scanning. The virus or malware can damage the PST file or encrypt the data that can cause inaccessible PST files and data loss.

Tip: To avoid PST corruption due to virus or malware, install a reliable anti-virus or anti-malware protection tool on your business laptop or system with the latest definitions and real-time protection to prevent such incidents. Also, use cloud storage to transfer data. If files are large, scan the drive and files before transferring.   

How to Repair a Corrupt or Damaged Outlook PST file?

To repair a corrupt, damaged, or inaccessible PST file, you can use SCANPST.EXE (also known as Inbox Repair Tool) or Outlook repair software, such as Stellar Repair for Outlook.

Inbox Repair Tool or SCANPST.EXE is suitable for small PST files (up to GB size) with minor corruption, while the Outlook repair tool can fix large or severely corrupt PST files with complete integrity and precision. It also provides advanced options to export the recovered mail items to a new PST file, Office 365, or Live Exchange Server.

Besides, Inbox Repair Tool repairs corrupt PST files by removing irrecoverable mail items that can lead to data loss. Therefore, always make a backup before repairing the PST file using Inbox Repair Tool to avoid such a situation. That way, you can still repair the original PST file with complete integrity using the Outlook repair software we mentioned.    

To Wrap Up

Outlook PST file corruption is evitable if you follow the best practices while using your Outlook account. Follow the tips and recommendations we have shared in this article to keep a check on your Outlook PST file and fix errors or issues before the PST file is damaged beyond repair. However, if the PST file gets damaged, you can use the SCANPST.EXE (Inbox Repair Tool) or an Outlook repair software, such as Stellar Repair for Outlook, to repair damaged or corrupt PST files and avoid permanent data loss. Unlike Inbox Repair Tool, the software can repair severely corrupt or encrypted PST files with complete integrity and without any file size limit.

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About The Author

Ravi Singh

Ravi Singh is a Senior Writer at Stellar®. He is an expert Tech Explainer, IoT enthusiast, and a passionate nerd with over 7 years of experience in technical writing. He writes about Microsoft Exchange, Microsoft 365, Email Migration, Linux, Windows, Mac, DIY Tech, and Smart Home. Ravi spends most of his weekends working with IoT (DIY Smart Home) devices and playing Overwatch. He is also a solo traveler who loves hiking and exploring new trails.