This article describes how to configure Microsoft Outlook to block attachment file name extensions that Outlook does not block by default. If you use Outlook in a Microsoft Exchange environment, you can configure the server to block certain attachment file name extensions by using the Outlook E-mail Security Administrator Package.

Additionally, this article includes information about how to customize your security settings for different Outlook configurations with and without Exchange.

Solution: -

How to customize your security settings to block additional attachment file name extensions

The following methods describe how to customize your security settings for different Outlook configurations with and without Exchange.

How to block attachment file name extensions in an Exchange environment with the Outlook Security Administrator Package

If you have an Exchange environment that uses the Outlook Security Administrator Package and you want to add more attachment file name extensions that you want to block in your Outlook configuration, you can add more attachment file name extensions to the Level 1 file list. To do this, follow these steps:

The next time that your users start Outlook, the new settings will be applied.

Note If you the Show Level 1 File Attachments check box from step 4 was already selected to allow all Level 1 attachment file name extensions types to appear in the e-mail message as an attachment, you must add the attachment file name extensions that you do not want to appear in the e-mail message as an attachment by following this one additional step:

For additional information about how to configure Outlook related security public folders in your Exchange environment, click the following article numbers to view the articles in the Microsoft Knowledge Base:

263297 (http://support.microsoft.com/kb/263297/) OL2000: Administrator information about the Outlook e-mail security update

290499 (http://support.microsoft.com/kb/290499/) OL2002: Administrator information about e-mail security features

Note Knowledge Base article 290499 also applies to to Outlook 2003.

How to block attachments in a non-Exchange environment

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 (http://support.microsoft.com/kb/322756/) How to back up and restore the registry in Windows

Use the information that is in this section if you are running Outlook in a non-Exchange environment and you want to block more attachment file name extensions than those that Outlook already blocks.

If you are using Outlook 2000, Microsoft Office 2000 Service Pack 3 (SP3) or later must be installed on your computer so that you can configure Outlook 2000 to block certain attachment file name extensions.

To obtain the latest service pack for Microsoft Office 2000, click the following article number to view the article in the Microsoft Knowledge Base:

276367 (http://support.microsoft.com/kb/276367/) How to obtain the latest Office 2000 service pack

If you are using Outlook 2002, Microsoft Office XP Service Pack 1 (SP1) or later must be installed on your computer so that you can configure Outlook 2002 to block certain attachment file name extensions. To obtain the latest service pack for Microsoft Office XP, click the following article number to view the article in the Microsoft Knowledge Base:

307841 (http://support.microsoft.com/kb/307841/) How to obtain the latest Office XP service pack

Outlook uses the Level1Add registry key to permit you to add additional attachment file name extensions types that you want to block.

To add additional attachment file name extensions types that you want to block, you must add the Level1Add key to the registry. To do this, follow these steps.

For Outlook 2000

Follow these steps, and then quit Registry Editor:

Notefile_name_extensions is a list of the attachment file name extensions. Each attachment file name extension is separated by a semicolon. For example, type .zip; .gif if you want to block both .zip and .gif files from appearing in the e-mail message as an attachment.

Outlook 2002

Follow these steps, and then quit Registry Editor:

Notefile_name_extensions is a list of the attachment file name extensions. Each attachment file name extension is separated by a semicolon. For example, type .zip; .gif if you want to block both .zip and .gif files from appearing in the e-mail message as an attachment.

If Outlook 2002 does not behave differently after you add the Level1Add registry value, click the following article number to view the article in the Microsoft Knowledge Base:

312834 (http://support.microsoft.com/kb/312834/) The "Level1Add" registry key is missing from Outlook 2002

Additionally, you can add additional attachment file name extensions types that you want blocked by using system policies to add the following registry key for Outlook:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\10.0\Outlook\Security

Outlook 2003

Follow these steps, and then quit Registry Editor:

Notefile_name_extensions is a list of the attachment file name extensions. Each attachment file name extension is separated by a semicolon. For example, type .zip; .gif if you want to block both .zip and .gif files from appearing in the e-mail message as an attachment.