Email Notifications

I'm trying to get my notifications working correctly. I am a system administrator and 5 others are system administrators. Out of 15 users I am the ONLY one that can receive notifications. Everyone of the users have there email address added to there User Profile. I have selected ALL on the days of the week and time of day to receive the notifications. I have also added people to projects and added comments and no one can receive notifications but me.

Can someone help me as to what I am doing wrong? I want others to see notifications when a ticket is assigned to someone or even if there is a comment, or some type of notification. PLEASE HELP!!!