popwatcher is a daemon that maintains a list of hosts that are authorized to use your mailserver as an SMTP relay based on those hosts successfully authenticating to your POP mail server. The default configuration is designed to work with qpopper and exim, but can be used with other mailers and POP servers.
MailWebForm allows you to send an email message from a Web site. It processes an HTML form, composes the email, optionally by processing a template, and delivers it. MailWebForm features spam protection in which the recipient's address is not specified in the HTML form, but rather uses property files to get the mail destination. Flexibility and ease-of-use are MailWebform's design goals. MailWebForm accepts three levels of parameter input: a global property file, user property files, and HTML form input. The setup is easily done through a administration Web site.
Spammilt is a sendmail-milter which scans email headers for blacklisted relaying servers and locally predefined blacklisted domains/words. By default, when spammilt detects spam, it adds a warning to the header and the subject. It's also possible to reject such emails without bothering the recipient.
JSpamfilter is software that intercepts connections from remote Internet mail servers before they can connect to your mail server. The originating IP address for the inbound connection is then checked against one of the DNS-based SPAM Blackhole (DNSBL) lists maintained on the Internet by various organizations. If the check passes, the connection is allowed to proceed to your mail server; if it fails, the connection is told that the mail server is unavailable, then dropped.
purepost is an interface between Courier-MTA and Sophie for virus scanning. You can have it check mail for all your users, or just a few. Using courier's dot-courier functionality, this script intercepts an email before it hits the mailbox, creates a temporary file, tells sophie to scan that temporary file for viruses, and if it finds a virus, denies delivery and notifies the sender (otherwise it allows the message to be delivered).
Net_NNTP is a PHP/PEAR library for communication with NNTP servers. Net_NNTP handles connection and protocol-level commands (RFC977), including many non-standard commands (RFC2980), via a user-friendly API which hides the actual NNTP commands/syntax. Some knowledge about NNTP and general knowledge about email and MIME is required, since parsing of content and headers is left up to the user. Net_NNTP allows advanced users direct usage of NNTP commands via the separate protocol implementation. Net_NNTP includes a fully-functional NNTP to HTML gateway demo application.