Telnet times out on local machine but works externally

Question

Im trying to get inbound mail working with postfix. Nothing is showing up, even in the maillog. Outbound works perfectly, but inbound doesnt. If i use telnet from an external server over port 25, i get a 200 status and it works. When i perform it from the local machine it times out. I have nothing that gets written to the log when i run telnet on localhost, so im not sure what the cause is.

I tried to disable the firewall systemctl ststus firewalld and this worked, but it still didnt work. There is a network firewall across the entire network, so its not a big deal turning this off. On the main network firewall i have opened port 25 to accept all inbound traffic. Are there other ports that should be opened?

Answer 1

You have two different problems.

One is that telnet 25 from local machine times out. That's probably a local firewall problem, or a NAT problem.

The second is that you're not receiving mail, with nothing in the logs, even though telnet 25 from an external machine "works". You do get something in the logs when you do that, right? This is a problem where people who want to send you mail are not contacting you. It is probably a DNS problem, but since you're not giving much information, I can't help you more than to say that on an external server, dig +short mx $yourdomainname should return $yourservername, and that telnet $yourservername 25 should arrive at your server.