help with iptables

[VGS]

Hi,

Add another remote server called C to the equation. C tries connecting 
to B:25 . B:25 forwards it to A:25 . A:25 should now send all reply 
packets to B which should then SNAT and forward the packets to C . This 
is needed for the connection to succeed. If A:25 sends packets directly 
to C, C does not know what to do with the packets as it is expecting 
packets from B and not A. Hope this helps you in making the changes 
necessary to make your setup work .

Regards,
Shinoj.




Dave Cramer wrote:

> Heres what I want to do
>
> I have a new mail spam filter machine I want to test before I change 
> the mx records
>
>
> this machine I will call A receives mail and forwards it to B
>
> currently B is the MX
>
> So what I'd like to do is  using iptables :
>
> route port 25 traffic currently going to B --> A except when it comes 
> from A
>
> I tried
>
> iptables -t nat -A PREROUTING -p tcp -m tcp -s ! A --dport 25 -j DNAT 
> --to-destination A
>
> but this didn't work
>
> suggestions ? 
>
> Dave



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