I don't quite understand the description of the scenario you gave, but the examples with telnet are the correct behaviour. You would normally only be able to hit services on the wan IP from outside of your network. in your example you connect to wan:25 from the client. This is then forwarded into your server. the server then sees a packet addressed to it from the client, and so replies *directly* to the client to establish a connection. however your client is expecting to talk to the wan ip, not the server ip, so disregards the response. Compare this to you wardriving and hitting wan:25 then that also hits the server, but the response is sent back to the internet ip address of your neighbors router, so goes back through your router, which then translates the ip back to the wan address and you then continue to establish a connection.
Last edited by acid_kewpie; 02-22-2009 at 09:52 AM.