libsrs2 is the next generation SRS library. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. When a message is forwarded, the sender address must be rewritten to comply with SPF policy. The Sender Rewriting Scheme, or SRS, provides a standard for this rewriting that is not vulnerable to attacks by spammers, is easy to parse by common mail filters, and handles multiple hops neatly and safely.
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.
SPF is a new strategy for preventing junk mail. The present SMTP standard for email allows anyone to forge anyone else's email address. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. libspf2 is a complete and robust implementation of SPF which provides support for many MTAs. Support for new MTAs is in progress.
spfmilter is a milter (sendmail mail filter) which implements the Sender Policy Framework (SPF). SPF is a strategy for preventing junk mail. The SMTP standard for email allows anyone to forge anyone else's email address. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it.
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.
Decimail Server is a mail server supporting IMAP and SMTP that uses a PostgreSQL database to store messages. Mailboxes are defined using SQL queries, allowing complex client-independent automatic message filtering and categorisation. For example you can partition your messages chronologically, by correspondent, and by mailing list at the same time, with each message appearing in several mailboxes. You can also use PostgreSQL's text indexing extension for fast keyword searching. Decimail also features anti-spam processing of outgoing messages.
qmail-spp provides plug-in support for the qmail SMTP daemon (qmail-smtpd). It allows you to write external programs and use them to check SMTP command argument validity. The plug-in can trigger several actions, like denying a command with an error message, logging data, adding a header, and much more.
odmrd is a server for the "On Demand Mail-Relay" protocol specified in RFC2465. It can be used as a standalone daemon or in inetd mode. It needs a MySQL server to store authentication and optional accounting information. It also requires a BSMTP-capable mailserver, such as Exim or postfix.
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.