Group of users

Like any email solution we can create groups of users. So my suggest is let user or Admin create group of user, so this "group" will work like a simple user (but with a lot of users)

When I type to write a new private message in user field I will see my groups there too.
This Groups could be two types: private and public

I am not suggesting "Organic groups" or something like this.

I am suggesting something like gmail have.
You can create groups of users and send email(private messages) to them (like gmail)

Hope be useful.

Cheers