NAT and NOTIFY messages

Hello!

I'm working on presence server using JAIN-SIP and I'm wondering if 
someone could give me some help with traversing through NAT.

I've got following quite basic SIPp flow:
Client                Server
REGISTER  ---------->
200       <----------
SUBSCRIBE ---------->
200       <----------
NOTIFY    <----------
200       ---------->

Currently responses (200) are going nicely through the NAT with UDP and 
TCP, but I'm unable to get NOTIFY messages through to the client.

Responses are sent by using server transaction and I've tested NOTIFY 
messages by using Dialog so far. I've also tried sending NOTIFY 
statelessly, but that fails naturally. I also tried setting 
CACHE_SERVER_CONNECTIONS and CACHE_CLIENT_CONNECTIONS to true, but 
didn't notice any difference.

What approach would be correct to handle sending of NOTIFY messages? The 
NAT mapping is planned to be kept alive by sending REGISTER messages 
often enough. I'm feeling that I'm looking in wrong direction at the 
moment or missing something pretty simple so little help would be 
appreciated.

I'm using latest JAIN-SIP 1.2 from CVS.

Best Regards,

- Lauri Tielinen