It is possible to share selected files with people who are not invited to the project as a project user. When sharing selected files, people who receive this e-mail will have access to the files via a link in the e-mail. This means that they get access to the shared file's version and thus do not receive notifications in the future in the event that new versions are uploaded.
When sharing selected files, the sender can also send a message along with the sharing and make the sharing of the files time-limited.