How to block all attachments in Outlook emails?

Author: Kelly Last Modified: 2025-01-20

Email attachments can sometimes pose security risks, such as viruses or malware. To protect your inbox, you may want to block all attachments or only allow specific file types. While Outlook has limited native options and cannot restrict attachments to only certain safe file extensions, Kutools for Outlook (KTO) provides a more advanced and flexible solution. In this tutorial, I’ll walk you through two methods to manage email attachments, including the powerful Set Save Attachment Extension feature in Kutools for Outlook, which allows you to receive only attachments with specific safe file extensions.

Block all attachments in Outlook emails

Set safe attachment extension using Kutools for Outlook

Block all attachments in Outlook emails

To block all attachments in Outlook emails, please do as follows:

1. Press Win + R keys simultaneously to open the Run dialog box, type regedit into the Open box, and click the OK button.

the screenshot of step about blocking all attachments in outlook emails 1

2. In the User Account Control dialog box, click the Yes button.

the screenshot of step about blocking all attachments in outlook emails 2

3. In the Registry Editor window, please open the Security key with below path:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
Note: Above path works for Outlook 2016. Please change the 16.0 in above path to 15.0 for Outlook 2013, or change to 14.0 for Outlook 2010.

4. Right click the Security key, and select New > String Value in the right-clicking menu. See screenshot:

the screenshot of step about blocking all attachments in outlook emails 3

5. Name the new string value as Level1Add.

6. Right click the new Level1Add string value, and select Modify in the right-clicking menu. See screenshot:

the screenshot of step about blocking all attachments in outlook emails 4

7. Now the Edit String dialog box comes out. Please paste below file extensions into the Value data box, and click the OK button. See screenshot:
.xlsx; .docx; .pptx; .pub; .xlsx; .docm; .pptm; .txt; .xlsm; .doc; .ppt; .ps; .xls; .dotx; .pdf; .xps; .xml; . dotm; .xps; .wtf; .mht; . dot; .potx; .emf; .mhtml; . pdf; .potm; .wmf; .htm; . xps; .pot; .gif; .html; . mht; .thmx; .jpg; .xltx; . mhtml; .ppsx; .png; .xltm; . htm; .ppsm; .tif; .xlt; . html; .pps; .bmp; .txt; . rtf; .ppam; .wmf; .xml; .txt; .ppam; .emf; .xls; .xml; .xml; .rtf; .csv; .odt; .mp4; .pptx; .prn; .wrg; .wmv; .odp; .dif; .xlam; .xlsx; .xlam; .slk; .pdf; .ods; .xps; .zip; .rar

the screenshot of step about blocking all attachments in outlook emails 5

Note: Most of extensions used in normal Outlook work are listed here. If you want to block other types of attachments, please add their extensions into the Value data box, and separate them by semicolons.

8. Restart your Outlook.

And now you will see all kind of attachments are blocked in Outlook emails. See screenshot:

the screenshot of step about blocking all attachments in outlook emails 6

Set safe attachment extension using Kutools for Outlook

Kutools for Outlook offers a more advanced solution with its Set Safe Attachment Extension feature. This tool allows you to block all attachments or only allow specific file types, providing greater control and security.

👉 Kutools for Outlook has a free version now, whose 70+ features are free for a lifetime. Download the Free Version Now.

Step 1. Download and install Kutools for Outlook, and click Kutools > Options.

Step 2. In the Options dialog, navigate to the Others tab. In the textbox labeled Set Safe Attachment Extensions for Receiving Emails, enter the file extensions you want to allow, using a semicolon (;) as the separator. And click OK.