An no-reply option for users

We have users that represent upstream systems. For instance an monitoring system. We currently configure an invalid email as primairy to prevent GLPI from sending emails back to the the system. It would be nice to have an 'no-reply' option in the userobject that will prevent GLPI from generating an actual email.

This will improve performance, reduce overhead, and will prevent a chain of NDRs being generated in the email environment.