One way would be to setup your own fileserver and use GIT for the exchange. Or use any of the GIT websites such as Gitlab or Github. Private repositories are usually a paid service. But Git is very flexible, and you can use it with any internet connected fileserver.
Another very simple way is to zip your project directory and mail it to someone else.
E-mail is an quite old fashioned protocol though and there is no (default) encryption for it.