Zimbra got a new lease of life after Telligent bought it over. I'm happy that development for Zimbra continues as our own mail server is Zimbra! :) We have been using it for years.
Recently, Zimbra releases Collaboration Server 8.0. We'll be looking forward to upgrading to this new and exciting version!
By the way, there are various deployment models to choose from when deploying Zimbra Collaboration Server.
Again, Cloud is a platform which software developers cannot choose not to support these days.