I am trying to telnet to my OpenSMTPD 6.0 mail server (Ubuntu 19), but I am consistently getting the error message:
telnet mymachine.xyz.com 25
telnet: connect to address XX.XX.XX.XX: Connection refused
I went through other tutorials and few of them said that it may be because my ISP would be blocking port 25. Now, I think I should now change the port number of OpenSMTPD to a new port number so that I can do a telnet. I have already allowed the port number through the firewall.