I have a microsoft exchange server that recently decided not to accept external mail. So I did a dns report check and it came back as failure to contact mail server on port 25. so I tried to telnet to the server on 25 (FQDN, internet IP) from outside my firewall, no luck. I checked the firewall settings and port 25 is fowarding to the correct internal address. I then tried telneting to server from inside firewall using both the FQDN, IP, and from the server with loopback, and i get the same cannot connect to server on port 25: connection failed.
the really interesting thing is that users can send mail internally, I did not configure this server so I have been playing catch up alot and I was hoping someone could give me an outsider point of view.
Any help or insight would be greatly appreciated.