My home network is set up as follows:
PCs -> Wired Network ---| |--- Server --- Internet PCs -> Wireless Network ---|
The server runs the fetchmail, postfix and dovecot daemons under Ubuntu to retrive e-mail from the ISP and store it on the server. E-mail is accessed from any of the PCs on the wired or wireless networks via an IMAP interface hosted on the server.
This all works great.
I'm about to let my young children use e-mail for themselves. But before I let them loose on the world, I wanted the server to implement a whitelist for e-mails that are retrieved from the ISP and sent to their mailbox. Ideally, the incoming senders full address should be listed in the whitelist for it to be forwarded to the mailbox. Anything that isn't in the whiltelist should be forwarded to a different mailbox which I can then look through and update the whitelist as appropriate.
How do I set up the various daemons to do this?