This KB will show you how to restrict users access to a distribution list In your Exchange organization.
In this example I’m going to allow only the Administrator user account to be able to send emails to a DL called DL_Manages.
To do it, Open EAC -> Groups and double click on the group or click edit.
In the group properties page go to Delivery management and tick Sender inside and outside my organization
Click on the + sign and add the account.