So we opened up port 25 for our mail server. I ran "lsof -i TCP:25 -n" and found atleast 60+ connections to other servers. Because of this, our mail server isn't able to send emails to external domains. I verify this by killing the PID of connection, but seconds later they reappear. During this 3-5 second span, my emails that were in queue were sent out. Anyways, I think there's a setting in the oracle install that will accommodate these additional connections but I would also like to know so that I can block them if possible. I have iptables enabled but the same IPs keep showing up!
essmo 7110 applmail 185u IPv4 410413 TCP 192.168.10.31:3030->18.104.22.168:smtp (SYN_SENT)
essmo 7110 applmail 186u IPv4 411288 TCP 192.168.10.31:3312->22.214.171.124:smtp (SYN_SENT)
essmo 7110 applmail 189u IPv4 410424 TCP 192.168.10.31:3033->126.96.36.199:smtp (SYN_SENT)
-A OUTPUT -d 188.8.131.52/255.255.255.0 -j DROP
-A OUTPUT -d 184.108.40.206/255.255.255.0 -j DROP
-A OUTPUT -d 220.127.116.11/255.255.255.0 -j DROP