smtp-gated is a transparent SMTP proxy supporting: NAT on Linux (netfilter), NAT on FreeBSD (ipfw and others getsockopt-compatible), or dedicated mode (separate/external machine). DATA traffic is spooled in write-thru mode and then scanned for viruses or spam. The program is transparent for TLS connections.

http://smtp-proxy.klolik.org/

-- LucaGibelli - 11 Feb 2007