Exchange 2013 redirect mail with PGP

I have a Exchange 2013 Server. Now as a User I want to redirect some Emails to an email address which is not in my Exchange Server.

But for security reasons I want that every email that will be redirected should be encrypted with the PGP Key of the receiver.

Is there any solution how I can solve this? Maybe with an Agent but I think that isnt possible. Maybe I have to setup up a small mail server for receiving the mail from the exchange than encrypt and redirect.