To prevent them from sending anything but local e-mail, you can use the Delivery Restrictions tab to set permissions on SMTP Connector. See KB article Q265293 for details on how to configure an SMTP Connector.
Dig Deeper on Exchange Server setup and troubleshooting
Related Q&A from SearchExchange Staff
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.