[CLUE-Tech] Sendmail and IPtables

[David Anselmi]

On Wednesday 02 October 2002 02:55 pm, you wrote:
[...]
>
> The strange part of this is that if I initiate a connection to xyz.com
> on port 25 from the firewall box I get a connection timed out but  If it
> comes from an internal ip lets say 192.168.x.x it gets the desired
> reults. This is not happening on every domain just a select few. I
> should give you some information on the box at this time.

Well, you can turn on logging to see if your rules are the problem.  You only 
need to look at the INPUT and OUTPUT chains, so put a -j LOG rule in that 
matches your DROP rules (before the DROP), and perhaps one at the end of each 
chain.

You can also run a sniffer on the outside network (and on the firewall 
listening to the outside NIC to be thorough).  That might be easier to 
understand.

If this is really only for some domains from the firewall itself, I'd say 
it's a network problem not firewall rules.  But you can post your rules to 
see if we can spot any that would only apply to some domains.

Is your firewall able to get MX records from DNS for the problem domains?

I assume you're using telnet or netcat to test the connections.

Dave