Microsoft Exchange/Office365 Windows

How to Block ZIP/RAR Attachments in Outlook

Block ZIP/RAR Attachments in Outlook 2016 – 2007
Block ZIP/RAR Attachments in Outlook

Microsoft Outlook is a widely used email client, but it’s not uncommon for spam emails to contain potentially harmful ZIP and RAR attachments. In this guide, we will walk you through a simple method to block ZIP and RAR attachments in Microsoft Outlook versions 2016 through 2007. By following these steps, you can enhance the security of your email communication and protect your system from potentially unsafe attachments. Also, see How to set up and Configure Office Online Server, and how to change Windows 11 and 10 default mail app to Outlook.

Here are other related guides: Clear Saved Email Address: How to stop Microsoft Edge from remembering your email ID, How to disable file download in Microsoft EdgeHow to stop Outlook from opening links in Edge Browserand How to Enable Internet Explorer Mode in Edge in Windows 11.

Step-by-Step Guide in Blocking ZIP/RAR Attachment in Outlook

Press the Windows key + R simultaneously to open the Run dialog box. Type “regedit” and press Enter to open the Windows Registry Editor.

Open run utility
Open run utility

Within the Registry Editor window, navigate to the following registry path, depending on your Outlook version:

For Outlook 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security

For Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security

For Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security

For Outlook 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Security

If you can’t find the Security key, right-click on the Outlook key and select “New” -> “Key.”

Create security key
Create security key

Right-click on the “Security” key in the left pane and select “New” -> “String Value.” Name the new String Value as “Level1Add” and press Enter.

Create a string value
Create a string value

Double-click on the “Level1Add” string value to modify it. In the “Edit String” dialog box that appears, enter the file extensions of the attachment files you want to block. Separate multiple extensions with a semicolon.

Enter outlook attachment extensions to block (E.g. Zip, RAR)
Enter outlook attachment extensions to block (E.g. Zip, RAR)

For example, to block both ZIP and RAR attachments, enter “.zip;.rar” into the “Value data” box.

Click “OK” to save your changes and close the Windows Registry Editor. To ensure that the changes take effect, restart your Microsoft Outlook application.

Please see Add or Remove Sites from Favorites: Microsoft Edge Guide, how to Pause Windows Update, and how to Disable Internet Explorer with Group Policy & Registry.


By following this detailed guide, you can effectively block ZIP and RAR attachments in Microsoft Outlook versions 2016 to 2007. This added layer of security helps protect your system from potentially harmful email attachments, ensuring a safer email communication experience. Be cautious when modifying the Windows Registry, and make sure to follow the steps carefully to avoid any issues.


Will blocking ZIP and RAR attachments prevent all potential security threats in Outlook?

While blocking ZIP and RAR attachments is a helpful security measure, it does not guarantee complete protection against all email-based threats. Cybercriminals can use various tactics to deliver malicious content. It’s essential to remain vigilant and employ other security practices, such as keeping your antivirus software up-to-date, avoiding suspicious emails, and being cautious with links and attachments, even from trusted sources.

Can I unblock ZIP and RAR attachments in Outlook if I change my mind?

Yes, you can unblock ZIP and RAR attachments in Outlook by revisiting the Windows Registry and removing the file extensions from the “Level1Add” string value. Simply follow the steps outlined in the guide, locate the “Level1Add” string value, and delete the extensions you previously added. Afterwards, restart Outlook for the changes to take effect.

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I hope you found this blog post helpful. Please let me know in the comment session if you have any questions.

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