- Open flagged attachments in Outlook that you consider safe
- Open blocked attachments in Outlook
- Tips for opening blocked file attachments
Open flagged attachments in Outlook that you consider safe
Microsoft Outlook blocks certain files from being opened by email. These blocked attachments in Outlook have file extensions associated with executable file types that may contain viruses. However, EXE files are not always malicious. Here’s how to change the settings to make Outlook open these files.
The instructions in this article apply to Outlook 2019, Outlook 2016, Outlook 2013, Outlook 2010, and Outlook for Office 365.
Open blocked attachments in Outlook
To prevent Outlook from blocking attachments, make changes to the Windows registry. If you’re not comfortable making changes to the registry, see the Tips section below to learn how to open blocked attachments without making changes to your computer.
To prevent Outlook from blocking malicious attachments, install an antivirus program on your computer and only open attachments from trusted sources.
Using the Registry Editor to Unlock Specific File Types:
Close Microsoft Outlook if it is open.
Open the Registry Editor.
Before you begin, you should know how to add, modify, and delete registry keys and values.
Find the registry key that applies to your version of MS Outlook:
Outlook 2019, Outlook 2016 and Outlook for Office 365:
HKEY_CURRENT_USER Software Microsoft Office 16.0 Outlook Security
HKEY_CURRENT_USER Software Microsoft Office 15.0 Outlook Security
HKEY_CURRENT_USER Software Microsoft Office 14.0 Outlook Security
HKEY_CURRENT_USER Software Microsoft Office 13.0 Outlook Security
Select Change † New † string value to create a new value called Level1Delete †
New > String Value”
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Open the new value and enter the file extensions you want to unblock. For example, to open EXE files in Outlook, go to the text box Data value and type .exe (including “.”). To add multiple file extensions, separate each extension with a semicolon, for example type .exe; .cpl .chm .bat to unlock EXE, CPL, CHM and BAT files.
Select Okay to save changes in the row.
Close the Registry Editor and restart your computer.
To revert these changes so that Microsoft Outlook will block these file extensions again, go back to the registry location you specified in step 3 and remove the value Level1Delete †
Tips for opening blocked file attachments
Microsoft Outlook blocks files based on file extension. Any file you receive that doesn’t use a potentially dangerous file extension will appear in Outlook without any error or warning messages.
For this reason, you can ask senders to email you files with a different extension, even if that’s not the actual extension for that file. For example, instead of sending an executable file with an EXE extension, they can change the suffix to .SAFE or another suffix 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 bypass Outlook restrictions and open blocked attachments is to send an email to the sender with the file in archive format. ZIP and 7Z are among the most common.
Using the archive format works because it’s the same as changing the file extension to something Outlook accepts (in this case .ZIP or .7Z), but it’s more convenient because you don’t have to change the file extension. A program like 7-Zip can open most types of archive files.