This class only sends the message via an SMTP server, it does not compose it.
The class that can be used to compose the message to send via SMTP with this class is the MIME message class.
phpclasses.org/mimemessage
It does not yet support body message encryption but it can be added. There are several standards for encrypting messages. Just send me an example of message that is encrypted the way you intend so I can see what is necessary.