I've a brand new install of centos 7, installed virtualmin.
Doing a test connection externally (telnet to port 25) I get 421 connect to smtp server, connection error 10060. I believe this means the connection timed out.
Using SSH to connect to the server and running the same command connects fine which leads to firewall settings being the issue.
I've looked at the default settings for firewalld and it appears that server smtp is allowed in the public zone (as installed by virtualmin). I've applied the configuration in case that is needed but it makes no difference.
Is there anything I'm missing?