Users of Microsoft Outlook have encountered a problem where they are unable to access email attachments. Specifically, they are unable to open attachments by double-clicking on them. Even attempting to right-click on the attachment and select the 'Save as' option proves ineffective. Instead, the application displays an error message - "Unable to Open Outlook Attachment." Even basic troubleshooting steps like restarting the Outlook application do not resolve the issue, leaving the attachment still inaccessible after the restart. What should you do next? No need for concern. In this blog, we will guide you through the steps to resolve this problem.

Error message look as below: Unable to Open Outlook Attachment

The most common reasons for facing such unwanted error message are:

  1. When a user's access is limited to temporary Internet files and folders on either the local system or the server, User is restricted to access temporary Internet files and folders

This issue arises when a subdirectory, housing standard duplicates of temporary internet files, has reached its storage capacity.

  1. Outlook restricts access to suspicious attachments as a precautionary measure based on its default security protocols. This is done to prevent potential damage to the user's Outlook database or other critical system files. As a result, Outlook automatically secures these attachments, potentially displaying one of the aforementioned error messages.
  2. If a user attempts to access Outlook attachments while the Outlook PST files are corrupt or inaccessible,
  3. When a user repeatedly opens the same Outlook attachment(s), multiple temporary files with identical filenames are generated in the Temporary file directory. Eventually, Outlook prohibits the storage of temporary files with identical filenames in the temporary location.
  4. If a user encounters difficulty accessing attachments in Office 365 via Outlook Web App, it means that Outlook Web App is preventing the opening of attachments with certain file extensions.
Solution to fix error:
Solution I: When the cause of the error is associated with Temporary Internet folders:
  • Step 1.Click Start, search, and select the Run option.
  • Step 2.Type regedit.exe in the Run box and click OK to open the Registry Editor. Click on Edit and then opt for the Find option. Click on Edit and then opt for the Find option
  • Step 3. Type OutlookSecureTempFolder in the Find dialog box and click the Find Next option. Type OutlookSecureTempFolder in the Find dialog box
  • Step 4.Locate the registry key that contains the actual folder location. It may appear like: Locate the registry key
  • Step 5.Now, note down the folder's location by double-clicking the key name on the right panel. Note down the folder's location
  • Step 6.Go to the Run window and type the particular location and click OK.
  • Step 7.The folder is automatically opened by the default browser.
  • Step 8.Remove all the files present in the folder.
  • Step 9.Restart your browser and try opening the Outlook attachments, which you were unable to access.

Note: You might want to consider disabling Outlook Add-ins, as external Add-ins could potentially be causing issues with accessing Outlook attachments.

Solution II: When the cause of the error is associated with default security protocols:

If the errors stem from security restrictions, the user will need to amend and reinstate the security settings in the Outlook registry. The process of modifying security registry keys varies depending on the version of MS Windows. Refer to the version-specific steps outlined by Microsoft recovery experts for guidance. We've outlined steps for both the oldest and most recent versions of the Windows OS.:

For the oldest version, Window XP:

  • Step 1.Click Start, search, and select the Run option.
  • Step 2.Type the following command and click OK. Type the command and click OK
  • Step 3.Welcome to the System Restore page will appear.
  • Step 4.Select Create a restore point and click Next.
  • Step 5.Now a new page will open, here mention the new file restoration location, and click create and subsequently click the Close button.
  • Step 6.Again, repeat Steps 1, 2, and 3.
  • Step 7.Select Restore my computer to an earlier time option and click Next.
  • Step 8.When the new page appears, select the system checkpoint. A list will appear, click "Guided Help (Registry Backup)," and select the Next button.
  • Step 9. A System restoration message will prompt, listing configuration changes made, click OK. The confirmation page will appear after it, click Next and OK button consequently.
For the latest version Windows 10:
  • Step 1.Click Start, search, and select the Run option. Type REGEDIT.EXE
  • Step 2.Mention administration password if password confirmation is prompted.
  • Step 3.After opening Registry Editor, trace the registry key that you want to modify.
  • Step 4.Now, Click on the File menu and then select Export. Click on the File menu and then select Export
  • Step 5.The Export Registry File box will appear, mention the place where you want to restore the backup name of the backup file to identify it afterward, and Click Save. Mention the place where you want to restore the backup
Solution III: When Outlook Web App does not open attachments

The Outlook Web Application has the capability to limit the downloading of files with particular extensions. We have the option to modify the policy settings to permit the necessary file formats.

If you encounter difficulties when attempting to download files with specific extensions through Outlook Web Application, you have the option to remove the file extension from the blocked application list and include it in the list of permitted extensions. To do so, please reach out to your Exchange administrator..


In this blog post, we addressed the challenges that users often encounter when attempting to download or access attachments in Outlook. We delved into the various underlying causes of this issue and presented corresponding solutions, offering step-by-step guidance for each remedy. If you find that the error persists despite these efforts, it may be necessary to repair your corrupted PST file. Rest assured, we have a reliable solution for you. Simply download and install the Kernel for Outlook PST Repair tool, and follow the straightforward on-screen instructions to rectify your PST file.