email ports forwarding w/ existing local email server.

Good day.

I have to forward email ports from local net to the whole world. At
the same time I have a local email server that functions too. -
Therefore I have I divide the requests between those coming to the
local one and those that go to the outer one.

Having said that I have:

world's net - 1.1.1.1

local net - 192.168.0.0/24

iptables firewall, w/ running email server - 192.168.0.1

eth0 - the world's net

eth1 the local one.

Here is how I try to accomplish this:

/sbin/iptables -A FORWARD -i eth1 -s 192.168.0.0/24 -p tcp -m multiport
--dports 25,110 -j ACCEPT

/sbin/iptables -t nat -A PREROUTING -s
192.168.0.0/24 -p tcp --dport 25000 -j DNAT --to-destination
______:25

/sbin/iptables -t nat -A POSTROUTING -i eth1 -s
192.168.0.0/24 -j SNAT --to-source=1.1.1.1

My questions are:

1. Is it all correct/safe in any way, or needs additional correction?

2. _______ - what should I use here in case I do not want to limit the
access to a single email server?

Thank You for Your time.

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