Hodge, You better pack your lunch for a couple of days from what I am seeing.
There are plenty of setups on this forum. I am not sure there is a one best way.
It depends on what they are doing.
With today's computers not being expensive and may be more expensive to keep running.
I would think of having two computers. Basically only because if they want a mail server and maybe having the mail server do some virtual machines for accessing the internet.
We do not let our workstations go to very many places on the internet that is not already approved. They are locked down.
We, I, am scared of viruses. I am here to stay, if i was not, well then who cares much.
We have databases worth millions. That is not to take lightly. When computers are down. You are down.
We have our lans double natted(two routers one behind the other). The main file server is behind the second router along with workstations.
We have computers for accessing the internet behind the first router. The second router is hooked up behind the first router. DMZ from the first router is pointing to the second router.
If you forward ports on the first router, then they will to any machine hooked behind the first router.
On the second router, you can forward only those ports to what machines you want. The firewall on the second router will provide protection to the workstations and the file server.
If you do not want to have computers setup behind the first router(between the first router and the second). You can even set up those virtual machines I was telling you about.
You can use SME with Virtual software or you can use PROXMOX and put your mail server(being sme) into a virtual machine and a couple of other operating systems on the first computer immediately behind the first router. Your backups for the first sme operating system should be light. You can access the first sme operating system between the routers.
You can use remote control software to access any computers or virtual computers from behind the second router.
You can setup the remote computers where you cannot transfer the files to the second sme server behind the second router.
IF you do not allow mail accessed by the workstations to the second server. You should be ok.
We do all this because i do not want to worry much about viruses on any workstation or server.
Have a good time during the St PATS weekend fellow.