Mail2sh makes it possible to carry out shell commands by email. Email is sent to a particular user on your host and the commands will be carried out if the user and password given matches ones in /etc/passwd. Commands are executed with the user's privileges, and combined with a PGP module ensures a certain level of security for use. Note that the system is not natively encrypted, so use of an encryption mechanism is highly recommended for security reasons.
redWall is a bootable CD-ROM firewall which focuses on Web-based reporting of the firewall's status. It includes Snort, snortsam, dansguardian, and support for fwbuilder, squidguard, reporting (using BASE/sarg/ntop/webfwlog), VPN (Openswan/PoPToP/Openvpn), Spam Filtering (spamassassin, dcc, razor2, clamav, amavis-new, dspam and maia mailguard), and mail-based, alerting. Configuration data are stored on a floppy or USB disk.
CRM114 is a Controllable Regex Mutilator and Smart Filter, designed for easy creation of filters for things like incoming email redirection, spam filtering, system logs, or monitoring processes. Filtering rules can be either hard-coded (such as regexes), soft-coded (calculated at runtime or read from an external file or process), or learned dynamically by phrase matching (as in Bayesian filtering, Markovian matching, Winnowing, or Hyperspatial classification). This makes it possible to create very accurate filters with very little actual work. Accuracies over 99.9% are achievable.
SeeYouLater's purpose is to fetch a list of IPs of known spammers and to ban them by putting them in /etc/hosts.deny. /etc/hosts.deny is usually read by xinetd or daemons using tcpwrapper. The software is composed of: the feeder, that looks at SMTP daemon logs for the string ++BAN:IP++ and feeds the database accordindly; and the butcher, that looks at the database and updates /etc/hosts.deny. You may want to run the butcher on a system that has no access to the SMTP logfiles, but you can install both packages on the same system. It has been written to run with Exim.
LMon is a package for near real-time monitoring of logs, sending email alerts upon known (rule hits) or unknown data (rule misses). It features buffering of multiple rule hits within a given interval, cap at a given maximum number of lines, wait for a given interval before sending next alert, and auto- discovery of log rotation. It can be run from the command line without configuration, or be controlled from a central configuration file with multiple instances monitoring different log files/sending alerts to different people.
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.