Microsoft Outlook users have reported an issue which prevents them from accessing the mail attachments. In this problem, users are not able to open Outlook attachments by double clicking on them. Right clicking the attachment and clicking on ‘Save as’ option also doesn’t seem to work. The application instead throws an error - “Unable to Open Outlook Attachment”. Simple hacks like restarting your Outlook application doesn’t fix the issue and attachment remains inaccessible even after restart of application. What to do next? Well, no need to worry. We will take you through this blog to help you fix the issue.

Error message look as below:


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

  1. When a user is restricted to access temporary Internet files and folders on the local system or on the server.

This error occurs when sub folder, which contains default copies of temporary Internet files, has reached its storage limit.

  1. Due to default security protocols, Outlook denies permission to access suspicious attachments, which may harm user’s Outlook database or other system files severely. Thus the Outlook attachments get automatically locked displaying either of the above displayed errors.
  2. When user tries to open Outlook attachments while Outlook PST files are in corrupt or inaccessible state.
  3. When a user repetitively access the same Outlook attachment(s). In this case, multiple temporary files carrying the same filename are created in the Temporary file folder. After a certain period, the Outlook platform denies to save temporary files of the same filename at the temporary location.
  4. When a user is not able to access attachments through Office 365 using Outlook web app. Outlook web app blocks attachments having some specific file extensions.


Solution I: When the cause of error is associated with Temporary Internet folders:

  • Step 1.Click start and select run option.
  • Step 2.REGEDIT.EXE will appear, click on Edit and then opt Find option.
  • Step 3. Type OutlookSecureTempFolder in the Find dialog box.
  • Step 4. Locate the registry key that contains actual folder location. It may appear like:

  • Step 5.Now, note down the folder’s location.
  • Step 6.Go to Run option in the Start menu and type the particular location and click OK.
  • Step 7.The folder be automatically opened by 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.

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

If the errors are result of security restrictions then user must edit and restore the security settings in the Outlook registry. Now, medication of security registry keys depends upon the MS Windows version. Check out the steps to modify these keys version wise provided by Microsoft recovery experts. Here we have described steps for the oldest and the latest versions of Windows OS:

For the oldest version Window XP:

  • Step 1.Click start and select run option.
  • Step 2.Type following command and click OK.

  • Step 3.Welcome to 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 Close button.
  • Step 6.Again, repeat step 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 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 and select 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 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 afterwards and Click Save.

Solution III : When Outlook web app doesn’t open attachments

Outlook web application can restrict download of files with some specific extensions. We can change the policy settings to allow the required file types.

If you are facing issues while downloading files of specific extensions using Outlook Web application; you can remove a file extension from blocked application list and add it to allowed lists. For this, contact your Exchange administrator.


In this blog we discussed the issues faced by users while downloading or accessing attachments using Outlook. We discussed various causes behind the problem and the solutions based on those causes. We provided step-by-step instructions for each of the fixes. If however, you are still not able to get rid of the error, you need to repair your corrupt PST. Don’t worry, we will provide you the best solution for this as well. Download and install the Kernel for Outlook PST repair tool and fix your PST by following simple on screen steps.