[exim] Restricting the use of the From field

I have a satellite configuration with MS Exchange as the smarthost. Any
mail from any user in Debian server will make Exim to authenticate to
Exchange as the Exchange user set up in passwd.client. So that, any user
will be able to send mails as any of the valid email addresses set up in
Exchange for the Exchange user.

Is there a way to restrict the From field for the users in the Debian
host? Is there any other better setup?

Thanks in advance