The Outlook E-Mail Security Update (included in Office 2000 Service Pack 2 and later versions) blocks access to .exe, .com and a number of other "dangerous" file types. You can't open these files from Outlook, nor can you use Outlook to save them to your system. If you try to forward a message containing such files, Outlook does not include the attachment in the forwarded message.
Here is how open access to such blocked attachments using the Windows Registry (always make a backup before editing the registry):
1. Start > Run > type: regedit
2. Navigate to the following 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)
3. Under that key, add a new string value named: Level1Remove
4. For the value for Level1Remove, enter a semicolon-delimited list of file extensions you want to allow. For example, entering this:
.reg;.mdb;.url
would unblock registry files, MS Acces files and internet shortcuts. Using the leading dots may be required by new security patches. There should be no spaces between extensions.
5. Restart Outlook
If you are using this registry entry, the Outlook Help > About MS Outlook dialog should contain "Security Mode: User controlled" above the license information.
Note: To force users to save *.zip files to the hard drive before opening, add .zip to the extensions in step 4.
The above applies to Outlook 2003, Outlook 2002 and Outlook 2000 SP3 (but not Outlook 98 or earlier Outlook 2000 versions)
Alternatively, you can use this Outlook add-in tool: Attachment Options
