You mention “all ports”, does that mean that any service port is available through the router to this machine or that you have all of the Jive Messenger ports opened?
Connecting to external IP vs. Internal: you want users outside the router/firewall to access the server with the external IP or did you mean you want clients INSIDE the router/firewall to use the external IP address to connect (i’‘m not familiar with linksys, but depending on the firewall and how it handles xlate tables, you might not be able to use external IP’'s to connect internally)
Can you try to port scan from the outside back to this server and verify that the router actually has the ports open? (there are several web services that will scan for you)
when you resolve the domain name from the inside are you resolving the outside IP or the internal IP? (nslookup from a command prompt)
I suppose my main question is really for clarification of the first part. who is supposed to use the external IP? clients inside the router/firewall or clients outside the router/firewall