POPauthd is a Perl-based daemon that uses POP to authorize connecting hosts for SMTP relaying. It is particularly useful to authenticate roaming users with IP addresses that change often. The daemon runs in the background, watching the syslog for successful POP logins. When it sees one it enters the IP in sendmail's access database, giving the host authorization to relay through the server. The entries can be expired after a prescribed, configurable period of time with a companion script run via crontab.
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.
COMDOM Antispam is a high-capacity platform designed for the requirements of ISPs and other large organizations that must fight spam. COMDOM is a powerful anti-spam system operating as a stand alone mail gateway with relay control, authentication, and load balancing support. The system consequently can be used together with mail servers or as a stand alone gateway for several mail servers. The robustness, flexibility, and the high data throughput capacity of COMDOM Antispam allow for the software to be deployed for a range of solutions.
Designed as a Perl framework to support many different types of POP and email servers, Mobile POP Relay is useful for mobile users. Once a user successfully authenticates against a POP server, relaying is allowed through the server for a specified time period. It supports Ipop3d, Qpopper, and Vpopd with Sendmail or Exim.
Buni Meldware Communication Suite is an enterprise groupware product providing an email server, calendar server, and a Web mail client. The Web mail portion is written using Adobe's Flash and provides a rich cross-browser experience. Protocol support includes IMAP, POP, SMTP, iCAL, WCAP, and more. It uniquely supports full database email storage as well as file system storage of emails on major database platforms, and is easily installed via a Web Start graphical installation process.