GLD-NG is a greylisting daemon for Postfix. It is a fork of GLD which introduces some new features. It adds IPv6 support, and therefore relies exclusively on PostgreSQL, due to its better support of IP addresses. A basic Web UI is included to manage the greylist.
OpenProtect is an anti-spam server that filters spam and blocks viruses, phishing, and other malware. Acts as an SMTP gateway and integrates with any email server like Postfix, Sendmail, qmail, Exim, Microsoft Exchange, Lotus Domino, Zimbra, etc.