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.