RPC over HTTP security issue

[nawalmiftahi () gmail com]

Hii All,
 We are considering for deploying RPC overHTTP for remote connection to our exchange , but the issue we are facing is 
if we deploy this RPC/HTTP.ALL our active directory users can remotely access the exchange by providing their 
credentials,but we does'nt want to give access to all but only to few specific users. presently we have outlook 
webaccess ,access to which is given only to specific users..can anyone let me know how we can deploy this by giving 
access only to the specific users .