Howtoforge posted a new howto about installing Zimbra Collaboration Suite (ZCS) on Ubuntu
This guide shows how to install the Zimbra Collaboration Suite (ZCS) on Ubuntu 6.10 (Edgy Eft) and 6.06 (Dapper Drake) server systems. Zimbra is a full-featured, open source collaboration suite - email, group calendaring, contacts, and web document management and authoring. It has a feature-rich AJAX web interface and is compatible with clients such as Microsoft Outlook, Apple Mail, and Novell Evolution so that mail, contacts, and calendar items can be synchronised from these to the ZCS server. It can also be synchronized to many mobile devices. ZCS makes use of many existing open source projects such as Postfix, MySQL, and OpenLDAP.How To Install Zimbra Collaboration Suite (ZCS) On Ubuntu