keep messenger communication internal only

Hello, I am deploying IM through my exchange 2000 server. Most IM clients
will be the old windows messenger 4.7 which is fine, but is there a way to
keep the communication internal. When starting windows messenger you have 2
options: .net messaging service or exchange messaging service. I want to
restrict my users to just having the exchange messaging service option. How
can I prevent them from choosing the .net messaging service and talking with
anyone on the internet?
I appreciate any suggestions. Thank you. Phil

I'd also like some information about this topic as we're looking at deploying
an internal IM system.

"Phil" wrote:

> Hello, I am deploying IM through my exchange 2000 server. Most IM clients
> will be the old windows messenger 4.7 which is fine, but is there a way to
> keep the communication internal. When starting windows messenger you have 2
> options: .net messaging service or exchange messaging service. I want to
> restrict my users to just having the exchange messaging service option. How
> can I prevent them from choosing the .net messaging service and talking with
> anyone on the internet?
> I appreciate any suggestions. Thank you. Phil