Bind and Postfix

Bind and Postfix

Post by shrin » Sat, 08 Apr 2006 15:03:47



Friends.

Today, i configured bind dns and postfix mail server for my network.

dns works well i.e name resolves well.
the command host <hostname> gives proper answer.

But, the command dnsdomanname gives nothing.

The posfix works only with the server.
the port 25 is not visible from client systems.
but the mail sent for internal users works well.

so, i suspect the problem may be in dns.
how to get the dnsdomainname command work?

Thanks,
T.Shrinivasan.

 
 
 

Bind and Postfix

Post by shrin » Sun, 09 Apr 2006 13:15:06


Hi Davide.

Quote:> Something make me thing that you have a) a firewall blocking connection
> from other systems to your smtp or b) postfix bind on 127.0.0.1 only.

There is no firewall running.
i have given that "inet_interfaces=all"

How to check that it binds only on 127.0.0.1?
is there any way?

Thanks,
T.Shrinivasan.

 
 
 

Bind and Postfix

Post by David Efflan » Sun, 09 Apr 2006 22:24:05



Quote:> Today, i configured bind dns and postfix mail server for my network.

> dns works well i.e name resolves well.
> the command host <hostname> gives proper answer.
> But, the command dnsdomanname gives nothing.

"hostname" should just show just your hostname, "hostname -f" should
show your full hostname.domain, and "hostname -d" should be just the
domain part (same as dnsdomainname).

> The posfix works only with the server.
> the port 25 is not visible from client systems.
> but the mail sent for internal users works well.


"localhost" is always yourself (127.0.0.1 loopback).  So you certainly

e-mail address.  You need some other hostname (unique from other PC's in
your domain) which /etc/hosts and DNS should point to an IP on your box
(possibly ethernet nic IP if static), or when I was on dialup with no
static IP I assigned my hostname to another loopback IP 127.0.0.2.

To see what IP:port postfix is listening on use "netstat -atn".
Local 0.0.0.0:25 means it is listening on port 25 of any interface. If
local is 127.0.0.1:25 that might be a default postfix setting for your own
safety.  Check for inet_interfaces setting in postfix's main.cf (maybe at
/etc/postfix/main.cf).

Foreign 0.0.0.0:* means it accepts a connection from any IP and
port.

Quote:> so, i suspect the problem may be in dns.
> how to get the dnsdomainname command work?

That might be based on the hostname.domain in /etc/HOSTNAME (not sure, it
simply works for me).  Just be aware that network scripts may set that
file during boot or when bringing up an interface, so you may need to look
for a HOSTNAME setting in network related scripts.
 
 
 

Bind and Postfix

Post by noEM » Sun, 09 Apr 2006 22:24:16



> Hi Davide.

>> Something make me thing that you have a) a firewall blocking connection
>> from other systems to your smtp or b) postfix bind on 127.0.0.1 only.

> There is no firewall running.
> i have given that "inet_interfaces=all"

> How to check that it binds only on 127.0.0.1? is there any way?

> Thanks,
> T.Shrinivasan.

Any way to test if your mail server software only bind to 127.0.0.1 ?

Sure! you can use the netstat command. Usually located under /bin/netstat.
Netstat can show the connection that are open for use and the currently
opened connections.

The syntax would be

netstat -a -n -u -t -w

The switches :

-a show All port ready for connection(s)
-n no name resolution (DNS)
-u show UDP "connection(s)"
-t show TCP connection(s)
-w show raw connection(s)

And if you only want to filter for mail (SMTP) port,

netstat -a -n -u -t -w | grep :25

If I may, a word of caution...

Running an open SMTP server on the Internet without a firewall
need some Very careful configuration. Not doing so is a guarantee
that some spammers will find your server and use it to relay its
own spam instead of your mail.

That might be a problem to you :

1) the resources in disk use, CPU time and network use will all
be consummated by someone else.

2) Sending spam (or Forwarding it) is a good way to end up on a
black hole list. Once inserted on such a list, may other mail server
so configured will find that your server is to be ignored and
suddenly you will end up with a much less mail that you wish
and a lot more mail that you do not...

So take a good look at configuration and firewalling...

For firewall, an easy program to configure firewall rule
is FireStarter. It's an graphical front end that will
help you build your rules. It is is available at :
http://www.fs-security.com/

Well I hope it help.

 
 
 

1. Hardware recommends for ipchains, postfix, squid and bind

Hi,

does anyone have experience in running a LINUX firewall on 486
hardware?
Is it realistic to use e.g. a 486/66 for securing a network from
20 to 120 clients with ipchains, running a mail relay
with postfix, Bind and Squid.

Thanks for help
Christian

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