How to stop sending emails to some users

Hello Everyone,

I don't want to send emails to few users (like Inactive users, some users left the company). there is any way or setting for stop sending email to selected user. I know we can add custom method and call before sending email from all workflow, conversion task, methods, life cycles but we don't want to update everywhere. Any one know how we can do this?

In User Itemtype there is a property "mail_stop" any one know, how its works?