How to Connect two networks

Hi all,

I need some help if someone could be kind enough please...

I'm currently studying and have an exam coming up and looking at the paper there's a part that's got me stumped

the scenario calls for me to set up 2 small networks each network consisting of:

A 2003 server

2 XP client machines that will allow users to send/receive emails to and from other users..........

I can configure the servers as mail and email users on the same network but I'm stuck on the following:

"Configure Network A to allow limited access by nominated users on Network B"

and

"Configure email to allow email communication between all users on both networks"

All of the above is being done in a virtual environment using Oracle Virtualbox so using a router isn't an option for me, I have read that RRAS will enable this but we haven't covered RRAS in the course yet and I don't have a clue.

This is what I did so far but ran into to brick walls

I "added" a 2nd adapter on my virtual server then set different static IP addresses for both, and both NIC's are on an "Internal Network" as are the clients:

"Local Connection - Static address 192.168.10.10"
"Local Connection 2 - Static address 192.168.20.10"

I configured RRAS with static routes as follows

Local connection
192.168.10.0
255.255.255.0
192.168.10.10
metric 1

Local connection 2
192.168.20.0
255.255.255.0
192.168.20.10
metric 1

but I cannot get any communication between the server and either of the clients, I tried assigning relevant static IP addresses on the clients so they'd be on the same networks "192.168.10.11 & 192.168.20.11"
but still nothing

can someone tell me what I'm doing wrong please

Thanks in advance

Jon