can you screen print your routers web page?
...anyway, there is usually a specific page for port fwd...make sure you didn't mess with the port fwd for a "application" for your computers IP address (thats actually easy to screw up)
if it were me, I'd use 81 and end in 81, and make sure the IP cooresponds to the Apex ...you might also "open" port 25 in your DMZ for whatever that same Apex IP is (I say this tenativley as I have no clue how your firewall or security is setup)