I’ve spent a few hours trying to get microsofts official windows mobile emulator working, even used an xp vm, and successfully got oz mobile installed, but it needs a cell connection to allow connection, but the fake emulated one from microsoft wouldn’t connect to the phone.
Also I’ve found from that forum post that oz is the company that provided this service for phones and released it for both tmobile and att. and the only difference between the two is the server it connects to.
Tmo
wirelessvillage.t-mobile.com
wirelessvillage.yahoo.t-mobile.com
wirelessvillage.icq.t-mobile.com
Att
aol.cwmim.com:1171
msn.cwmim.com:1175
yahoo.cwmim.com:1174
I assume the ips also change because it tracks billing or something. Att phones would be desirable because the domain cwmim is for sale which means theoretically any old phone you have could connect to im without any modification 
Though if you need to change it then it should be fairly simple, maybe by setting dns?
I’ve gathered from some reading that this uses sms to talk and only really uses data to update the buddy list and login. from looking at the empty servsmsaddr I can assume that the server sends out the sms number that it texts to, meaning we could use any number or email without modifcation.
Also the proxy address as seen in the picture above is used for mms so you can send pictures. It would need changing for non att carriers if you want mms.
EDIT EDIT-----------------------------------------------------------
I found out it uses the wireless village standard to connect.
The server is downloadable at http://www.nowimp.com/download/IMPServer.exe
nowimp.com has more information and documentation on how to use. As of now I am not able to figure out how to host properly. Using their client I was not able to connect. My settings are likely wrong or I’m doing something else wrong.
Also it uses custom transport layers as addons which you can find in the documents on their main page or in the installed software documentation. Sadly the transports are jabber which means no phoenix or escargot untill they implement it. We are able to make our own transport layer and could connect it to whatever we want still. The benefits of this (wireless village) are that many old phones automatically support it in their im, some phones even let you add servers yourself, there are also j2me and http clients.
The basic instant messaging still works, so it could still be used as its own im client, but that’s not desirable ik.
If anyone wants to play around with this, and get farther than I’m able, I’ll happily redirect the cwmim domain to your ip so we can test on unmodified att phones.
