Minimal Postfix SMTP proxy

Postprox is an excellent, simple tool very much in the spirit of *nix - it does a simple job, and does it extensibly. If you've been frustrated with the heavy, clunky nature of amavis and other spamc/clamdscan wrappers, or if you want to implement custom mail-handling features quickly and easily, postprox will get the job done, and get it done well. I've been using postprox in production for several years now, and it's never disappointed me.