Maxim Dounin Wrote:
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> For your particular task, it may be easier to configure raw TCP
> proxy to a particular 3rd party SMTP server (e.g., using nginx
> stream proxy,
> http://nginx.org/en/docs/stream/ngx_stream_core_module.html)
> or a full-featured STMP server with a smarthost configured.

Simple example 2 interfaces balanced backend limited to a vlan routed gateway:

stream {
error_log logs/stream_error_smtp.log;

upstream backendsmtp {
server 192.168.28.21:25;
server 192.168.28.22:25;
server 192.168.28.23:25;
}

server {
listen 25;
proxy_connect_timeout 30s;
proxy_timeout 30s;
proxy_pass backendsmtp;
allow 192.168.29.1;
deny all;
}

}

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nginx for Windows http://nginx-win.ecsds.eu/