Hi Nicole, The exact types of notification emails will lead you to the answer. Which are they? I suspect that the issue might lie in the templates (if you're using them) to create the projects. Sometimes if the template was created from an existing project, there can be members of the "project team" included on each project, even without being assigned to any tasks. Then if someone sends a message to the project team, they will receive it.
Regards, David Cornwell