We have an Exchange Server 2000 SP3 running in our main office. It is running on a 192.168.1.x network. We have some field offices connected through a Cisco VPN back to our office, and they are using 192.168.2.x, 192.168.3.x etc.
Although Messenger (Ver5.0) works great inside our main office lan, whenever we try to use it at a remote site it will sign in but not allow us to send messages either way. It just says the message could not be deleivered.
It may also be worth mentioning the PCs at the remote sites are not part of the main domain, but are part of a local workgroup.