HM2K

When a business I know had trouble with their broadband I was fortunately able to get them back online by using the redundant mobile broadband on the router.

The only issue then was that they couldn’t send email on port 25 through the Three mobile network.

The solution is to change the outgoing SMTP from port 25 to port 587.

Because I keep forgetting myself, here’s how you do it on cPanel:

You can run Exim on another port by going to the Service Manager in WebHost Manager and then enabling exim on another port and choosing the port number.

If it’s still not working, your firewall (iptables) is probably blocking it, so here’s what you need to do:

First find the iptables for port 25:

root@server [/]# iptables-save | grep “port 25”
-A INPUT -i venet0 -p tcp -m tcp –dport 25 -j ACCEPT
-A INPUT -i venet0 -p tcp -m tcp –sport 25 -j ACCEPT
-A OUTPUT -o venet0 -p tcp -m tcp –sport 25 -j ACCEPT
-A OUTPUT -o venet0 -p tcp -m tcp –dport 25 -j ACCEPT

Once you have that, copy each line and replace 25 with 587 and enter those in, like so:

iptables -A INPUT -i venet0 -p tcp -m tcp –dport 587 -j ACCEPT
iptables -A INPUT -i venet0 -p tcp -m tcp –sport 587 -j ACCEPT
iptables -A OUTPUT -o venet0 -p tcp -m tcp –sport 587 -j ACCEPT
iptables -A OUTPUT -o venet0 -p tcp -m tcp –dport 587 -j ACCEPT

Finally, you should check it works by using telnet from another machine:

[user@server2~]$ telnet mail.server.example.com 587
Trying 1.2.3.4…
Connected to mail.server.example.com (1.2.3.4).
Escape character is ‘^]’.
220-server.example.com ESMTP Exim 4.69 #1 Fri, 26 Nov 2010 16:54:07 +0000
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.

If you see a message similar to the above it has worked, so now you can save iptables and restart the service:

• iptables-save
• service iptables restart

Done!