net-mail@gentoo.org
Net-Mail
spamdyke is a filter for monitoring and intercepting SMTP connections between a
remote host and a qmail server. Spam is blocked while the remote server
(spammer) is still connected; no additional processing or storage is needed.
In addition to all of its anti-spam filters, spamdyke also includes a number of
features to enhance qmail.
Best of all, using spamdyke does not require patching or recompiling qmail!