I would like postfix to send all emails received on SMTP off to an external process, which will decide whether to allow them through as normal, or whether to put them into the hold queue (or another quarantine area), where they have to wait for admin approval.
I was thinking of doing this with an after-queue content filter, which uses pipe(8) to run a script on each message, and the script itself will spawn "postsuper -h " if it decides to put the message on hold.
Then the admin can do postsuper -d or -r to delete or pass the message on as appropriate.
So, my questions are - a) will this work, and b) is this the best way to do it? Would a milter or another type of content filter be a better approach?