How to Block Email Attachments

Blocking certain email attachments help stop viruses from spreading.

Email attachments are often the source of viruses. As a result, Microsoft Outlook automatically blocks attachments containing numerous file extensions. Users running Outlook without Microsoft Exchange may enhance existing security by modifying system registry settings. These modifications will prevent Outlook from delivering email attachments containing restricted file types.

Things You'll Need

• Microsoft Outlook 2003 or higher

Instructions

Outlook 2003

1. Click "Start" and then click "Run."

2. Type "regedit" and then click "OK."

3. Browse to the following registry key: "HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Security" and click once to select. If there is no "Security" folder listed you can create one by right-clicking the "Outlook" folder, clicking "New," followed by "Key." Name the folder by typing "Security."

4. Click "Edit," followed by "New," and then click "String Value."

5. Type "Level1Add" and then press the "Enter" or "Return" key.

6. Click "Edit" and then click "Modify."

7. Type the file name extensions you wish to block, separated by a semicolon. For example, type ".zip;.tif;.gif" to block these file types.

8. Click "OK."

9. Exit the Windows Registry Editor.

Outlook 2007

1. Click "Start" and then click "Run."

2. Type "regedit" and then click "OK."

3. Browse to the following registry key: "HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Security" and click once to select. If there is no "Security" folder listed you can create one by right-clicking the "Outlook" folder, clicking "New," followed by "Key." Name the folder by typing "Security."

4. Click "Edit," followed by "New," and then click "String Value."

5. Type "Level1Add" and then press the "Enter" or "Return" key.

6. Click "Edit" and then click "Modify."

7. Type the file name extensions you wish to block, separated by a semicolon. For example, type ".zip;.tif;.gif" to block these file types.

8. Click "OK."

9. Exit the Windows Registry Editor.

Outlook 2010

1. Click "Start" and then click "Run."

2. Type "regedit" and then click "OK."

3. Browse to the following registry key: "HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security" and click once to select. If there is no "Security" folder listed you can create one by right-clicking the "Outlook" folder, clicking "New," followed by "Key." Name the folder by typing "Security."

4. Click "Edit," followed by "New," and then click "String Value."

5. Type "Level1Add" and then press the "Enter" or "Return" key.

6. Click "Edit" and then click "Modify."

7. Type the file name extensions you wish to block, separated by a semicolon. For example, type ".zip;.tif;.gif" to block these file types.

8. Click "OK."

9. Exit the Windows Registry Editor.

Tips & Warnings

• Back up the registry before making changes.

• Follow these steps carefully as modifying the registry incorrectly may cause serious problems.

References

• Microsoft: How to Configure Outlook to Block Additional Attachment File Name Extensions

Resources

• Microsoft: Blocked Attachments in Outlook
• Microsoft: How to Back Up and Restore the Registry in Windows XP