Networking :: Forward SMTP Packets From Web Server To Another Machine?

I've a webserver at 10.10.0.55. Above in the hierarchy are managed network cisco switch / router and ASA firewall (the usual stuff). I also have a mail server at 10.10.0.200. I was told by the network admin that he can't forward port 80 to webserver and port 25 to mail server. Basically he said that it's a one-to-one (external.ip-to-internal.ip) mapping and all traffic, no matter what port it's destined for must go to 10.10.0.55. So, I turn to the wonder that linux is. The webserver is running Centos 5.4. Currently, all packets on port 25 are coming to the webserver. I want to forward all these packets to the email server. Note: the webserver only has one interface: eth0. I turned to web for help and did this in iptables:

Code:

$IPT -A FORWARD -p tcp -s 0/0 -i eth0 -o eth0 -d 10.10.0.200 --dport 25 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

It didn't work. I am assuming that since I only have one interface, a simple rule to the filter table and forward chain will not work.So i use the NAT table and try the following:

Code:

echo 1 > /proc/sys/net/ipv4/ip_forward
$IPT -t nat -A PREROUTING -p tcp -i eth0 --dport 25 -j LOG --log-prefix PortForward: --log-level 7
$IPT -t nat -A PREROUTING -p tcp -i eth0 -d 68.***.26.*** --dport 25 -m state --state NEW,ESTABLISHED,RELATED -j DNAT --to-destination

[code]....

First of all, since there is no service/daemon listening on port 25 on the webserver, is it even going to work? Isn't the webserver simply going to discard packets on port 25? I am assuming that packets go through the iptables first, and so iptables should route the packets to the email server, where there is postfix listening on port 25. Am i right? Also, as you can see in the code above, all packets coming on port 25 on the webserver should be logged. But they aren't. In order to troubleshoot, I'd like to at least know that packets are coming into the iptables. But since it's not logging, I can't find out what's wrong.