CPanel EXIM error – remote_smtp defer (111): Connection refused

On a cPanel dedicated server, exim was unable to deliver emails and all the emails were stuck in mail queue. Here what we found in the exim_mainlog

2009-03-22 03:46:04 H=localhost (Server-IP) [127.0.0.1] Warning:
Sender rate 0.0 / 1h
2009-03-22 03:46:04 1LlJJk-0003cX-HY <= test@somedomain.com H=localhost (Server-IP) [127.0.0.1] P=esmtpa A=fixed_login:test@somedomain.com S=798 id=1853.17.23.12.34.1237711564.squirrel@Server-IP
2009-03-22 03:46:07 1LlJJk-0003cX-HY alt3.gmail-smtp-in.l.google.com [209.85.218.31] Connection refused
2009-03-22 03:46:10 1LlJJk-0003cX-HY alt4.gmail-smtp-in.l.google.com [209.85.221.10] Connection refused
2009-03-22 03:46:10 1LlJJk-0003cX-HY == ourtestmail@gmail.com R=lookuphost T=remote_smtp defer (111): Connection refused

While troubleshooting the issue, we found the following:

root@server [~]# iptables -nL

Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- 0.0.0.0/0 127.0.0.1 tcp dpt:25
REJECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
reject-with icmp-port-unreachable

You have to remove this two iptables rules.

root@server [~]# iptables -D OUTPUT 2
root@server [~]# iptables -D OUTPUT 1

You then have to save iptables and restart.

root@server [~]# /etc/init.d/iptables save
root@server [~]# /etc/init.d/iptables restart

Now, check your mails and you will see all the mails getting delivered.