Un-tick all email alerts options in the "Email Alerts" section of the project home page. As Gemini admin set the "Email Item Resource" setting to "Yes" in the Notifications section of the Administration menu. This will add each resource as an item watcher and will send the watcher every update regardless of their preferences.

In version 4.0 users can configure email alerts for each project by any item, only items they have created or items they are assigned to. So they can decide to only recevie alerts for "item created" only when it is assigned to them.