S/MIME interoperability with external clients:

This policy setting controls whether Outlook decodes encrypted messages itself or passes them to an external program for processing. If you enable this policy setting, you can choose from three options for configuring external S/MIME clients: - Handle internally. Outlook decrypts all S/MIME messages itself. - Handle externally. Outlook hands all S/MIME messages off to the configured external program. - Handle if possible. Outlook attempts to decrypt all S/MIME messages itself. If it cannot decrypt a message, Outlook hands the message off to the configured external program. This option is the default configuration. If you disable or do not configure this policy setting, the behavior is the equivalent of selecting Enabled – Handle if possible.

No explicit registry values are set for enabled or disabled states.

• User
  Always use TNEF formatting in S/MIME messages

  Windows7
• User
  Check for the user's private key when the user sends an encrypted email that includes the user as a recipient

  Windows7
• User
  Do not check e-mail address against address of certificates being used

  Windows7
• User
  Do not display 'Publish to GAL' button

  Windows7
• User
  Do not provide Continue option on Encryption warning dialog boxes

  Windows7
• User
  Enable Cryptography Icons

  Windows7
• User
  Enable Retrieval of Remote Certificate Authority Information

  Windows7
• User
  Encrypt all e-mail messages

  Windows7
• User
  Ensure all S/MIME signed messages have a label

  Windows7
• User
  Fortezza certificate policies

  Windows7
• User
  Message Formats

  Windows7
• User
  Message when Outlook cannot find the digital ID to decode a message

  Windows7