The Outlook E-Mail Security Update (included in Office 2000 Service Pack 2 and later versions) blocks access to .exe, .com and other “dangerous” files. See Attachment Security for a list of the affected file types. You cannot open these files from Outlook, nor can you use Outlook to save them to your system. If you try to forward a message containing an .exe file, Outlook does not include the attachment in the forwarded message.

With the rash of recent viruses using *.zip files to get past antivirus filters and bypass Outlook’s attachment block, you may want to add the zip extension to the Level1Remove key to force users to save zips to their hard drive before opening or block access to zip files completely by adding zip to the Level1Add key.

Solution:

Outlook 2007, Outlook 2003, Outlook 2002 and Outlook 2000 SP3 (but not Outlook 98 or earlier Outlook 2000 versions) allow the user to use a registry key to open up access to blocked attachments. (Always make a backup before editing the registry.) To use this key:

Run Regedit, and go to this key:

HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security (change 10.0 to 9.0 for Outlook 2000 SP3 or to 11.0 for Outlook 2003, 12.0 for Outlook 2007 )

Under that key, add a new string value named Level1Remove.

For the value for Level1Remove, enter a semicolon-delimited list of file extensions. For example, entering this:

.mdb;.url

would unblock Microsoft Access files and Internet shortcuts. Note that the use of a leading dot was not previously required, however, new security patches may require it. If you are using “mdb;url” format and extensions are blocked, add a dot to each extension. Note also that there is not a space between extensions.

If you are using this registry entry, a glance at Help | About Microsoft Outlook will show Security Mode: User Controlled above the license information. See OL2002 You Cannot Open Attachments for more information on this registry entry.

To force users to save *.zip files to the hard drive before opening, add .zip to the extensions step 3. See How to configure Outlook to block additional attachment file name extensions for more information.

If you prefer not to edit the registry directly, you can use one of the tools below to make the change; not all support both Outlook 2002 and 2000.

After applying this registry fix or using one of the tools, the user still has to save the attached file to a system drive before opening it. In effect, the fix rolls the attachment behavior back to Outlook 2000 SR-1, with its included Attachment Security Fix. An end-user cannot bypass this “save to disk” behavior and open the file directly from the mail message, though an Exchange administrator can.

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