MailSpammer is a simple mailing list manager for smaller e-mail lists, using procmail and Perl. MailSpammer does not require administrator access, aside from initial setup (creating e-mail aliases), and features subscription, unsubscription, moderation, and archiving. The goal is not to be a majordomo-alike mailing list manager, but instead to provide a lightweight way to handle basic list management tasks.
Twisted is an event-based framework for Internet applications. It includes a Web server, an SMTP/POP3 server, a telnet server, an SSH server, an IRC server, a DNS server, a generic client/server pair for remote object access (Perspective Broker), and APIs for creating new protocols. It supports integration with GTK+, GTK+ 2, Qt, Tkinter, wxPython, Mac OS X (PyObjC) and Win32 event loops. It also supports TCP, SSL and TLS, UDP, Unix sockets, multicast, and serial ports. Supported protocols include HTTP, FTP, SMTP, POP3, IMAP, TOC, OSCAR (AIM and ICQ), SSH, DNS, IRC, NNTP, Jabber, SOCKSv4, Telnet, SIP (for VoIP), and XML-RPC and SOAP using external packages. Most protocols are supported as both servers and clients.
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".
Liferay is an enterprise portal. It handles users and portlet drawing, has a full administrative interface, supports all the major databases and the main J2EE application servers, and has single sign-on capabilities and multiple language support. It uses Apache Lucene for document searching. A number of portlets are included, including a guestbook, a calendar, a mapping utility which uses Expedia, news, polls, a document library, and live stock information.