Email Notification Permisions

I am having an issue with the notifications. I have quite a complicated system which is made up of many different user permissions. Each set of user permissions is assigned a categroy that only they can see but for some reason at time when i post to say class 1 category, people who are assigned to class 2 will get the email notification.

Then when they try and log in it gives then a 404 error because they dont have the permissions. Is there a way to control for this, why are they getting the notifications if they dont have permision to the category it is being posted into?