Notifications can be disabled by users from their "your profile" page.
1. Go to settings > your profile;
2. Deselect email notifications.
Alternatively, any admin user can manage their teams' notifications.
1. Go to settings > profile > your team page;
2. Click on 'edit' next to the team member ;
3. Deselect email notifications.
Note: This will only disable the non-essential notifications.