Relay to only some users

[dvit77]

I have 20 users on my network, and also about 10 other people from outside my office with e-mails from my domain. Can I let them relay only authentificating with user and password, maintaining the relay prohibited to other non authentificated users.

Also this 10 users are defined in active directory as USERS, can I define them as only e-mail users, and avoid the option to allow them to connect to my domain for othe purposes?

Thanks for helping me!