Apache Qpid is a messaging broker that implements the latest AMQP specification, providing transaction management, queuing, distribution, security, management, clustering, federation, heterogeneous multi-platform support, and much more. It is extremely fast and aims to be 100% AMQP Compliant.
Synovel Collabsuite provides email, calendaring, and instant messaging solution for enterprises. It consists of a Linux email server with calendar and IM, a Web-based administration panel, a desktop client suite that runs on Windows and Linux, and AJAX-based Web mail access. It uses open standards for communications: IMAP, POP, and SMTP for email, CalDav for calendaring, and Jabber for IM.