Open Blocked Attachments in Outlook

Open Blocked Attachments in Outlook

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Microsoft Outlook blocks lots of files from being opened through email, and for good reason. Many file extensions belong to executable file types that can potentially carry viruses. The problem is that not all files that use a certain file extension are actually harmful.

For example, while the EXE file extension is a common way to spread files since they're easy to open and can be faked into looking harmless - and are therefore one of many blocked attachments in Outlook - they are actually used for legitimate reasons too, like for software installations.

A blocked email attachment will prevent you from opening attachments you receive through Microsoft Outlook. The following messages are commonly seen when Outlook blocks an attachment:

Outlook blocked access to the following potentially unsafe attachments

While the steps below are straightforward and easy to follow, they do look daunting at first glance. If you're not comfortable following them, skip down to the "Tips" section to learn about a different way you can open blocked attachments without needing to make any changes to your computer.

These instructions apply to Outlook 2016, Outlook 2013, Outlook 2010, and Outlook for Office 365.

How to Open Blocked Attachments in Outlook

This method can be used to specifically unblock certain files so that you can always receive them without the above warning.

Preventing Outlook from blocking harmful attachments can definitely be a bad idea for obvious reasons. Make sure you have a good antivirus program on your computer and that you only open attachments from people you trust.

  1. Close Microsoft Outlook if it's open.

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

    Screenshot of Registry Editor

Outlook 2016/365


Outlook 2013:


Outlook 2010:

  1. Navigate to the Edit > New > String Value menu item to make a new value called Level1Remove.

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

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

  4. Close Registry Editor and Outlook, and restart your computer.

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

See our article on how to add, change, & delete registry keys & values for more help.

Tips on Opening Blocked File Attachments

As you can already tell, Microsoft Outlook blocks files based on their extension. This means that any file you receive that isn't identified as harmful (i.e. that isn't using a harmful file extension) can be received 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 this list of blocked attachments.

Then, when you save the file to your computer, you can rename it 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 within an archive format. ZIP and 7Z are some of the more common ones.

This 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 even more appropriate since you can open it easier as an archive rather than having to change the file extension. A program like 7-Zip can open most archive file types.