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.
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.
Sendmail Extended Queue Groups is an m4 file that can be used to add extended queue groups to Sendmail 8.12.x. Extended queue groups allow administrators to choose multipe queue groups based on the sender, recipient, or sender and recipient pair. This improves upon the default plain queue groups feature, which can only operate on recipients.
qpsmtpd is a flexible smtpd daemon written in Perl. Apart from the core SMTP features, all functionality is implemented in small "extension plugins" using the easy-to-use object oriented plugin API. qpsmtpd was originally written as a drop-in qmail-smtpd replacement, but now it also includes an smtp forward and a postfix "backend".
elspy is a layer of glue code that enables you to write Python code to scan email messages at SMTP-time with the Exim MTA (mail transport agent). It also includes a small Python library with common mail-scanning tools, including an interface to SpamAssassin and a simple-but-effective virus detector.
WBL is a really simple tool that can be used in a .qmail file for managing a white/black list of email addresses. It serves as a pre-filter to allow known-good friends and associates bypass the usual gauntlet of filters. Note that WBL is not intended to be a spam filter, it is simply an easy-to-use whitelist/blacklist management tool that serves to keep email that you really want to see out of your normal filters.