I just save setup NAT with two internet connections (fedora core 3):

eth2 is one internet connection, default gateway (let's say

eth0 is another internet connection with bunch of static routes (national ip pool) for this example let's say there is only one static route to

eth1 is lan (

nat working fine, static route balance connections right as I which but problem is incomming connection (smtp for now or can be any other)

I have two mx records:

and :
-A PREROUTING -p tcp -m tcp --dport 25 -j DNAT --to-destination

when ip connect to all working fine but:
when ip connect to connection drop because (I supose) answer going to eth0 (

What I should do, why iptables didn't keep connection persists ?

Tnx in advance

P.S. i'm newbie in linux world
P.P.S. sorry about that english :)