Vmailmgr provides a virtualizing password-checking interface to qmail-pop3d, a delivery agent to automatically deliver mail within a virtual domain, and a set of tools to manage such a domain. It also has Courier IMAP support. It uses one uid per domain, and this user can fully administer the domain without needing suid access rights. Making it work is as easy as adding a line in qmail's virtualdomains file, and running a few commands.
Twoftpd is an FTP server that strives to be secure, simple, and efficient. None of the commands can cause execution of other programs, and the normal model of execution does a chroot to the logged in user's directory immediately after authentication. The name "twoftpd" comes from the fact that there are two parts to the server: an authenticating front end, which contains no file or data transfer code, and one of two back ends, which contain all the data transfer code.
CVM (Credential Validation Module) is a modular system for validating credentials and providing information about them, using either piped command execution, Unix sockets, or UDP as the data transport. It is designed to be simpler than other existing systems (like PAM and Courier's authentication modules) and yet adequately functional for the majority of tasks.
ezmlm-browse is a Web interface for browsing ezmlm-idx (version 0.40 or later) archives. The presentation is modeled from that of the ezmlm-cgi archive browser that is part of ezmlm-idx, but with several additions. However, the output is completely template-driven, so you can make it fit into your current Web scheme.
ezmlm-idx is an addition and patch to ezmlm, adding multi-message threaded archive retrieval, digests, remote administration, message and subscription moderation, subscriber-only restrictions, message trailer, subject prefix, subscriber name storage, customizable setup, multi-language and MIME support, and more. In addition, it has improved bounce handling, case-insensitive subscriber address storage, and support for distributed lists (main and sublist are transparent to the subscriber). It can be compiled with MySQL or PostgreSQL support.