Saké Mail is a very high performance Web-based email system, designed for scaling to large numbers of concurrent users. It takes advantage of the Java Servlet API's memory-resident architecture and multi-threading HTTP response model. It avoids file system accesses through memory caching at every possible point, and never needs to touch the file system at runtime at all if coupled with an IMAP server. It supports POP3, IMAP, and SMTP, including authenticated SMTP. It also provides an extremely sophisticated message rendering system that can easily handle even complex HTML encoded messages with attachments that have been forwarded multiple times.
NullLogic Groupware is a modular Web-based groupware and email system designed for contact management and event scheduling. Additional features include private messaging, public discussion forums, webmail, shared bookmarks, file sharing, call tracking, order processing, an XML-RPC API, and integrated POP3 and SMTP servers.
Scalix Community Edition Raw (CE Raw) is functionally equivalent to Scalix's Community Edition software except that its components are individually available, making it easy to customize. It includes manual installation instructions via a community Wiki, with links to required third-party components. It is available for the Debian Linux distribution as well as Red Hat and SUSE Linux. The intent is to make it easy for Linux system admins, developers, and enthusiasts to to adapt an email and calendaring system for their needs and the needs of the community.