Last Updated on May 8, 2026
You may have noticed or been aggravated by the fact that Outlook won’t allow you to open or save certain types of file attachments from your email.
You may frequently see a warning message in your email that says “Outlook blocked access to the following potentially unsafe attachments”.
Outlook automatically blocks certain attachments that it considers unsafe for you to open, such as executable programs or script files.
Microsoft did this to try and prevent the spread of viruses through email messages.
While this security feature is helpful, it may also make things harder for you when you cannot get the legitimate attachments you need from your coworkers or clients.
Why Outlook Blocks Attachments
Microsoft originally came out with the Outlook Email Security Update for Outlook 98 and 2000 to help stop the rampant spread of email viruses.
This update was integrated into Office 2000 Service Pack 2, and all newer versions of Outlook now have this strict security built directly into the program itself.
Because of this, files ending in extensions like .exe, .vbs, .bat, and .mdb are blocked by default.
How to Unblock Attachments Using the Registry
You can perform a quick registry edit for modern and legacy versions of Outlook that will allow you to permit access to these blocked attachments.
Before doing any registry editing, be sure to make a backup of your registry first just to be safe.
Step 1: Click on your Windows Start button, type “regedit” into the search bar, and hit Enter to open the Registry Editor.
Step 2: You will need to browse to the following key path:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
Step 3: You will need to change the “16.0” number in that path to match your specific version of Outlook.
Use 16.0 for Microsoft 365, Outlook 2021, Outlook 2019, and Outlook 2016.
Use 15.0 for Outlook 2013, 14.0 for Outlook 2010, and 12.0 for Outlook 2007.
If you are on an older legacy system, use 11.0 for Outlook 2003, 10.0 for Outlook 2002, or 9.0 for Outlook 2000 SP3.
Adding the Allowed File Extensions
Step 4: Once you are in the correct Security folder, you need to add a new string value named Level1Remove.
Step 5: You can do this by right-clicking in a blank spot on the right side of the window, choosing New, and then selecting String Value.
Step 6: Type in exactly Level1Remove for the name of this new string and hit Enter.
Step 7: Right-click your newly created Level1Remove string and choose Modify from the menu.
Step 8: Enter a list of the specific file extensions you want to allow, making sure to separate them by semicolons with no spaces.
For example, you can type .exe;.vbs;.mdb into the Value Data box to force Outlook to allow those specific file types.
Step 9: Click OK, close the Registry Editor, and restart Microsoft Outlook for the changes to take effect.
Safer Alternatives to Unblocking Attachments
Modifying the registry to allow potentially dangerous files can sometimes leave your computer vulnerable to malware.
If you only need to receive a blocked file once, there are much safer alternatives than changing your global security settings.
You can ask the sender to compress the file into a ZIP folder before emailing it to you.
Outlook will always allow ZIP files through the security filter, and you can easily extract the executable file once it is safely on your hard drive.
Alternatively, you can ask the sender to upload the file to a cloud storage service like OneDrive, Google Drive, or Dropbox.
They can simply email you a secure download link instead of attaching the raw file directly to the message.
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