To configure message delivery restrictions, do the following:
- Open up user properties or group properties, select the Mailbox tab, and click Delivery Restrictions.
- Configure Accept messages to accept messages from a limited list of users and reject all others.
- To reject emails from external (non-authenticated users), select Require that all senders are authenticated.
- Configure Reject messages to reject messages from a limited list of users and accept all others.
- Configure Maximum recipients for sent messages to limit the number of recipients the user can send to.
- Configure Maximum size for sent messages to limit the size of emails the user can send.
- Configure Maximum size for received messages to limit the size of emails the user can receive.
- Click OK twice to apply the settings.
