OL2002: Recipients Cannot Read Messages When 168-Bit (3DES) Encryption Is Enabled

By default, Microsoft Outlook 2002 defaults to 40-bit (RC2-40) encryption when another encryption algorithm is not available. If you configure Outlook to default to 168-bit (3DES) encryption instead, and then you send a message to an e-mail client that does not support that encryption algorithm, the recipient is unable to read the message.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.


If the UseAlternateDefaultEncryptionAlg value exists under the following registry key, Outlook is configured to use a different default encryption algorithm: If one or more recipients cannot read messages that you send when Outlook is configured in this manner, remove the UseAlternateDefaultEncryptionAlg value so that Outlook defaults to 40-bit (RC2-40) encryption. To do so:

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. Locate and click the UseAlternateDefaultEncryptionAlg value under the following registry key:
   HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security
4. On the Edit menu, click Delete, and then click Yes.
5. Quit Registry Editor.