Open Blocked Attachments in Outlook

Open flagged attachments in Outlook that you deem safe

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Microsoft Outlook blocks certain files from being opened through email. These blocked attachments in Outlook have file extensions that belong to executable file types that potentially contain viruses. However, files with the EXE file extension are not always harmful. Here's how to change the settings so that Outlook opens these files.

Instructions in this article apply to Outlook 2019, Outlook 2016, Outlook 2013, Outlook 2010, and Outlook for Office 365.

How to Open Blocked Attachments in Outlook

If you want to prevent Outlook from blocking attached files, make changes to the Windows Registry. If you're not comfortable making changes to the Registry, skip to the Tips section below to learn a different way to open blocked attachments without making changes to your computer.

If you prevent Outlook from blocking malicious attachments, install an antivirus program on your computer and only open attachments from trusted sources.

To use the Registry Editor to unblock certain file types:

  1. Close Microsoft Outlook if it's open.

  2. Before you begin, you'll need to know how to add, change, and delete registry keys and values.

  3. Locate the registry key that pertains to your version of MS Outlook:

    Screenshot of Registry Editor

    Outlook 2019, Outlook 2016, and Outlook for Office 365:

    HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security

    Outlook 2016:

    HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security

    Outlook 2013:

    HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security

    Outlook 2010:

    HKEY_CURRENT_USER\Software\Microsoft\Office\13.0\Outlook\Security
  4. Select Edit > New > String Value to make a new value called Level1Remove.

    Screenshot of Edit > New > String Value
  5. Open the new value and enter the file extensions you want to unblock. For example, to open EXE files in Outlook, go to the Value data text box and enter .exe (including the "."). To add more than one file extension, separate each extension with a semicolon, for example, enter .exe;.cpl;.chm;.bat to unblock EXE, CPL, CHM, and BAT files.

    Screenshot of new string value
  6. Select OK to save the changes to the string.

  7. Close the Registry Editor and restart your computer.

To undo these changes so that Microsoft Outlook will block those file extensions again, return to the Registry location listed in Step 3 and delete the Level1Remove value.

Tips on Opening Blocked File Attachments

Microsoft Outlook blocks files based on the file extension. Any file you receive that isn't using a potentially harmful file extension appears in Outlook without any error messages or warnings. 

Because of this, you can request that senders email you files using a different file extension even if it's not the real extension for that file. For example, instead of sending you an executable file that uses the EXE file extension, they can change the suffix to .SAFE or anything else that isn't in the list of blocked attachments.

Then, when you save the file to your computer, you can rename the file to use the EXE file extension so that you can open it normally.

Another way to get around Outlook's restrictions and open blocked attachments is to have the sender email the file in an archive format. ZIP and 7Z are some of the more common ones.

Using an archive format works because it's the same as changing the file extension to something Outlook will accept (.ZIP or .7Z in this case), but it's more convenient since you don't have to change the file extension. A program like 7-Zip can open most archive file types.