I have setup my SMTP server (on a Linux/Ubuntu 15.04 VPS rented at OVH) according to http://www.binarytides.com/install-postfix-dovecot-debian/ (so there is no traditional user on the box; hence it looks like a naive installation of procmail is not relevant)
Any clues about adding some spam filter using free software only (with an ideological preference for GPLv3+ or LGPLv3+ ones)?
Some additional wishes:
I would like a possible web interface (to unblock some emails filtered as spam) but I profoundly dislike PHP. My web server is nginx.
I probably am interested in also using spamoracle (or some Bayesian machine learning filter).
I am willing to code a tiny thing which could help.
I'm a bit afraid to do wrong. It is an active server for my family MX domain @starynkevitch.net and I am getting all my personal emails there, and it is also used by my family (about a dozen persons).