I finally have my “ideal” mail system up and running. Everything goes into a “wait” queue which is cleared on a regular basis. Only white-listed mails are moved to my Inbox.
Bye-bye spam!
Of course, I need to review mails in the queue periodically to make sure I am not about to purge valid mails, but considering how spam mails seem to bypass most spam filters, I feel this solution is more resilient that blacklisting (but yeah, not fully foolproof).
Using: qmail + courier_imap + procmail + RoundCube
And yeah, currently have to white-list by adding entries manually in .procmailrc, but will get off my ass and hack the RoundCube interface to GUI-fy this.