IPTables Newbie

[bill at billhorne.homelinux.org (Bill Horne)]

On Mon, Nov 24, 2003 at 02:14:38PM -0600, Michael White wrote:
> Hello All,
> 
[snip]
> I'm building an RH9 firewall/mailserver combo box for a small
> client.  Sendmail appears to be running correctly in that I'm able
> to telnet to port 25 from an internal system.  However, after
> performing the following commands, I'm unable to telnet to the same
> port from and external IP:

> IPTABLES -A INPUT -p tcp --dport 25 -j ACCEPT
> IPTABLES -A INPUT -p ucp --dport 25 -j ACCEPT
> 

> Am I going about this all wrong?  Should I be entering the command
> differently?

It's probably not an iptables issue. The default setup for sendmail 
restricts it to listening for connections from the "localhost" only, 
since it's usually used only for outgoing mail.

Check the /etc/mail/sendmail.mc file, and search for the loopback 
address, which is "127.0.0.1". If you find it, remove the 
"Addr=127.0.0.1" option (it's a good idea to copy the line, and 
put "dnl" in front of the original to "comment it out", and then 
make your changes to the copy).

You'll need to do a "make" after the change; just follow the 
example at the top of the file. After you create the new 
sendmail.cf, restart sendmail and you should be set.

HTH.

Bill Horne