[Solved] Error “Outlook PST was not cleanly closed by the last program that used it”

Summary: System upgrades, abrupt Outlook application shutdown, oversized data files are some of the common reasons which may cause Outlook error: “Outlook PST was not cleanly closed by the last program that used it.” And the outcome is that the user is unable to access the Outlook profile in Microsoft Outlook 2019, 2016, 2013, 2010, 2007, 2003 and earlier versions. Here you can find the solution to resolve this error quickly:

For Microsoft Outlook to run uninterruptedly, it is essential to perform proper maintenance and monitor the size of Outlook PST files, because even minor faults may cause an Outlook profile to become inaccessible. And once the user is stuck, there is only one way to resolve the issue – repair the outlook PST file. 

The following reasons may cause the error: Outlook PST was not cleanly closed by the last program that used it:

  • Abrupt System Shutdown: The system shuts down abruptly either due to power failure or forced system closure even before the end of all applications (Microsoft Outlook).
  • Installation of External software: External software or third-party tools try to plug extra add-ins in the Outlook profile to enhance the user experience. These additional add-ins can become a significant cause of Outlook error.
  • Corruption in Outlook Data Files: Corruption in PST file may lead to Microsoft Outlook crash.
  • Virus or malicious software attack: Any virus or malicious software attack renders the Outlook profile inaccessible.

Resolve the error: ‘Outlook PST was not cleanly closed by the last program that used it.’

Method 1: Archive, clean or compact large PST data:

  • Archiving the mailbox items (including data from all folders) reduces the size of the PST file, which may help in resolving the error.
  • You can also cleanup your Inbox and organize your emails by using the various tools on command bar to ‘Sweep’, ‘Archive’ and ‘Move-to’.
  • Compacting the PST file and using Inbox rules also helps in resolving the Outlook error. Compact the current PST file and save the compacted file at an alternate location.

Note: Microsoft Outlook runs ‘Sweep Rules’ once in a day, and the ‘Inbox Rules’ are applied as soon as an email arrives in the mailbox.

Method 2: Repair PST by using Scanpst.exe:

Note: Scanpst.exe may result in data loss hence, take a backup of PST file before starting with the manual repair process.

  1. Close Microsoft Outlook and start the Scanpst.exe. Check the Outlook version and Windows OS version to locate the inbuilt utility, as different versions have different locations. It may be difficult to locate the Inbox repair tool without knowing the specific Windows OS and Outlook versions.
  2. Browse for the PST file to be repaired. All PST files are available with .pst extension
  3. Click the Options button and provide the Scan Log option
  4. Click the Start button. If the utility detects an error, then the file prompts to start the repair process.
  5. Click Repair button, and the Outlook utility will start the PST repair process

Scanpst.exe may not always be effective in resolving ‘Outlook PST was not cleanly closed by the last program that used it’ error, due to limitations like:

  • Cannot repair PST files that are more than 2 GB in size
  • Unable to repair PST file with severe corruption
  • Sometimes may result in data loss during the repair process

An Outlook Recovery software like Stellar Repair for Outlook can help overcome these shortcomings of scanpst.exe and provide a more efficient solution in case an Outlook PST was not cleanly closed and gets corrupted.

Method 3: Microsoft Outlook Repair Software

Outlook repair software selects the PST file and repairs the corrupt elements. You can save the corrected data as a new PST to reduce further chances of corruption.

  • Install the Outlook repair software such as Stellar Repair for Outlook.
Free Download
  • Select and scan the PST file.
  • Verify the repaired data from the free preview and save as new PST.

An option to split the repaired PST allows users to split PST as per size or date. This functionality helps to reduce further chances of corruption. The software can also be used to compact the PST file.    


Microsoft suggests taking the preventive measures for upkeep of the Outlook application, but most users seldom follow them. As a result, the Outlook user profile becomes corrupt and inaccessible due to the Outlook error: “Outlook PST was not cleanly closed by the last program that used it.”

The preventive measures help only till the time the error doesn’t affect the profile. Once the MS Outlook application gets stuck, it becomes imperative to use corrective solutions to repair Outlook data files.

As archiving and cleaning PST and Scanpst.exe may not help resolve the error in every instance, it is recommended to have an Outlook repair software as a more comprehensive solution.
Software such as ‘Stellar Repair for Outlook’ help resolve the problem and check PST file corruption by compacting or splitting the file. The software also saves the Outlook data as a backup in PST file and other formats after the repair process.

  1. Tom burner October 16, 2019
    • Eric Simson October 16, 2019
  2. Marry August 25, 2019

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