Hi,

I want to use a relay host on port 10025. No matter what firewall rules I use, the port is blocked. I tested this using  2 computers with local connections only. (Isolated from the overall network by unplugging the router and plugging both computers into the same switch). The tests involved using telnet to target ports. Error was  "connection refused." Port scans show different, but in important respects, similar results.

Way back in the days of inetd and xinetd, you told the daemon to fire up a program whenever a port was accessed. I cannot find an analogous process with SL. 

I use postfix as my MTA. The relay host is properly defined in the configuration file (main.cf). (This configuration worked with Ubuntu and with Mint Linux.)

OS version is SL7, up to date, running firewalld, fail2ban (b/c of brute force root attack) with SELINUX active.  

Thank you,
m hansel