Sharing and calendar requests

[R_1]

Hi

We have a rule that students cannot email each other. I have sent a few rules on the server that stop this (Exchange Server 2010)

However, they are still able to send messages via calendar sharing or journal sharing.

 

Does anyone know how to block these through rules or any other way?

Thanks in advance.

[sukh]

calendar sharing as in sending a message appointment/meeting or just sharing out their calendar?

 

also list steps for journal, I suspect it's the message class however need to look into this....