Maverix is an AOLserver module that implements the SMTP protocol and acts as an SMTP proxy with anti-spam and anti-virus capabilities. It includes a Web interface to manage quarantined messages and an administrative interface based on OSSWEB. Supported anti-spam software includes SpamAssassin and DSPAM, and supported anti-virus software packages are ClamAV and Sophos. Features include whitelisting, greylisting, and blacklisting, periodic digests with quarantined messages, a challenge/response mechanism, POP-auth, and short-TTL URLs for digests.
MFilter is a replacement for maildrop/procmail and fetchmail/getmail. It is an email retriever that supports Maildir or command delivery and processing. Its secondary goal is to facilitate the life of the network administrator by centralizing the downloading, filtering, and classification of mail in a simple and flexible way. Some of its features include XML file based configuration and logging of each action taken.
Protector is an add-in for Sendmail and other Unix mail servers that strips attachments types that could contain viruses or other "active content" from incoming email. It works on the pessimistic but safe paradigm of only allowing specified attachment types through; all others are blocked.
smtpfilter is a filter for an SMTP session which passes the session through transparently in real time, except for the DATA command which is intercepted in order to scan the data for spam and/or viruses with the scanner of your choice. The sources are heavily commented. The default spam filtering is a hybrid approach that uses spamassassin to self-train the excellent spamprobe Bayesian filter which works on a per-site rather than per-user basis. The virus checking can use clamav or NAI, or any other command- line scanner.
LOAF (List Of All Friends) is an extension to email that lets you send out address book data without compromising your privacy. It appends a hash-like data structure to each outgoing email, and collects similar attachments from the people who write to you. These files can be queried to see if they contain a given email address, but they can't be reverse-engineered to reveal the list of addresses used to construct them. LOAF lets you check whether someone emailing you for the first time is a complete stranger, or appears in the address books of some of your trusted correspondents. And as a decentralized application, it offers an interesting alternative to current social networking sites like Orkut or Friendster.
webfilt is not a spam filter, but provides a generic web-based interface for Bayesian-style Unix filters that need occasional training and corrections. It has been tested with SpamProbe and SpamBayes, but should work with other command line filters too. The webfilt system works with existing UNIX accounts, and consists of three distinct components that operate independently: User's procmail recipes and cron jobs; the webfiltd daemon; and webfilt.cgi, the Web interface.