[CentOS] Need help to track an ip port problem

[Steve Rigler]

On Mon, 2007-08-20 at 10:52 -0500, Erick Perez wrote:
> Hi, My centos 4.4 fully updated is going to be used as a mail server.
> However I did something or i didn't do something and I need some assistance.
> You see, If I run sendmail in port 25, i can telnet localhost 25 fine.
> but if I telnet the machine from another machine, the port is refuse.
> So i tested by running other programs (one at a time) listening to
> port 25, I cant connect.
> 
> So It seems that something is blocking specifically port 25 to receive
> incoming connections.
> 
> Can I have some assistance as to where to look for a configuration
> mistake? Basically something has my port 25 blocked on the same
> machine. BTW iptables is not running.
> 
> Cheers,

Generally speaking, "netstat -tpln" will list all listening tcp ports
and the process that has them open.  In your case, I'd bet that sendmail
is probably only configured to listen on lo.

-Steve