Instant Messenger services

[mwmm]

Hello All,

Is it possible to allow only local messaging using the Exchange Instant Messaging Service? I would like users to be able IM with co-workers, but eliminate the possibilty of IM'ing outside the domain.

I suppose I could also do this from a port blocking standpoint if need be, but woul like to eliminate it from the messaging server if possible.

Thanks inadvance

mwm