Proofpoint Encryption Desktop

Proofpoint Encryption Desktop is an email encryption Plug-in for Microsoft Outlook.
You will be prompted for the username and password of the mailbox that you are downloading Proofpoint Encryption Plug-in for.
When installed, the plug-in displays a Send Securely button in the Outlook interface that users can click to send secure messages.

The Send Securely button adds a header to the message that triggers a Proofpoint Protection Server rule to encrypt the message.