I have purchased one VPS. I am trying to run one postfix mail server. I already opened Port 25 (Postfix Port) in this VPS, ufw is the software for firewall. It seems port 25 is not open. Please explain. If you can provide the list of default ports open for a Linux Ubuntu VPS.
While trying to check it it says
# telnet 126.96.36.199 25 Trying 188.8.131.52... telnet: Unable to connect to remote host: Connection refused