This policy setting allows you to specify the formatting when sending S/MIME messages. If you enable this policy setting, ...

This policy setting allows you to specify the formatting when sending S/MIME messages.

If you enable this policy setting, Outlook always uses TNEF formatting when sending S/MIME messages.

If you disable or do not configure this policy setting, Outlook uses the format specified by the user when sending e-mail messages, including when sending S/MIME messages.