Hello all, I wonder if it is possible using Exchange Server to allow certain users "internal" email access, but disallow them from sending or receiving messages externally. Essentially, they will be able to email each other within our organisation but no one else. is this possible at all?Thanks in advance.

This can be done on your outbound smtp connector. On the Delivery Restrictions tab, the default is that no restrictions are applied to this connector. Alternatively, you can restrict the connector to specific users or reject messages from specific users.

http://searchexchange.techtarget.com/tip/0,289483,sid43_gci1103703,00.html

There are two KB may help you to work through the delivery restriction. Connector Delivery Restrictions May Not Work Correctly HOW TO: Configure Connectors to Reject Messages from Specific Senders in Exchange 2000 Server