I installed zimbra collaboration suite 7.1.1 open source on Ubuntu 10.04 LTS 64 bit server last June 18, 2011. I can send and received email and still looking for some improvements like adding disclaimer. The one that is on the wiki got some problem on 7.1.1. Still continuing to monitor the stability.
Release 7.1.1_GA_3196.UBUNTU10_64 UBUNTU10_64 FOSS edition.