[Serusers] NOTIFY header construction for mid-dialog presence event package

Hi all!!! I'm experiencing quite difficulties setting up a dedicated (and separated) presence server with NATted end-points and the dstblacklist feature. I'd like to get some info about the construction of the most important headers (Req-URI,Contact,To,From,Via,Routr) for the different NOTIFY modalities depending on the state of the subscription. Setting up async_auth_queries I've seen the pending and the active NOTIFY have different Req-URI and the second one is blocked by the NAT router. Further mid-dialog NOTIFYs providing changes in the presence status has also different headers... My main concern is whether the info for constructing the routing headers is taken from location table, from watcherinfo.dialog table, or from the incoming message...I know I could follow the code but an explanation would provide a really helpfull overview and later checking the code will be much simpler. Thanks in advance, Samuel.