I have to absolutely agree that OpenBSD using OpenSMTPD is "the right solution" for this problem. It's secure and after a little bit of learning, not hard to use.
Spamd is pretty effective for most spam. Not perfect, but what is now-a-days? You can monitor both sent and received emails. The delivery part raises the exact same questions for whatever you use, but dovecot is excellent and can work with whatever email programs you/they want to use on what devices. As far as privacy, others can give you help with that and scanning incoming and outgoing emails. Personally, I would send a copy to another user and scan without actually reading them yourself unless a "red light" shows up. That can be accomplished pretty easily and I did that myself when I had a set of mailing list emails processed before a script posted them to a forum board of received emails. i.e in from user joe, forwarded to joe2 and then scanning is done. IMHO, I would skip using partially insecure OS's like Linux. These are your kids! Chris Bennett
