Need recomendations on Chat software

Hi all

I have a customer that I manage their network. They recently asked me to recommend a IMChat software package for them.

First requirement is that they want to host the server in house. They do not want the users to sign up for AOL or MSN or anything like that for security reasons.

They have a Windows 2000 server and an Citrix server in the main office. The main server is a SQL2000 server.

Two they have 5 offices. One headquarters and 4 remotes they connect via a VPN tunnel to the main office and each location has an internal workgroup network. With different network IP's.

So they want to have all offices communicate with each other across the WAN and be able to IM each other without going to the Internet but across the VPN tunnels.


Does anyone have any recommendations on what kind of software is available to accomplish this?

 

That works well in a LAN but does it work across a WAN and a routed network?

I have seen products that put a fancy front end on Windows messenger but they say it only works in the local LAN