I used to have RoundCube on my servers and then I saw in a forum a suggestion to use Zimbra, from their web site the application looks, open-source, etc...
Man...What a dissapointment...Why on earth using Java? It's such a bad and heavy technology! I mean, come on, 1GB minimum requirement for RAM memory? 5GB HDD space? Oh, and it took a whole afternoon to have the beast to work on a CentOS server. Installation is very difficult and time-consuming compared to RoundCube. Why offering an open-source version if it's so difficult and badly documented that most people will be daunted and will use the commercial version? I don't know... There's something wrong. Why choosing such complicated technologies when you offer only additional features compared to RoundCube? I thing PHP 5 with an accelerator, or maybe mod_python2 would definately have been the way to go. Installing a php application is so easy, fast, and php applications run so fast, they need very little RAM... Also PHP development would have cost less money to Zimbra.
Zimbra also, from a user standpoint is cluttered... Too many graphics to load. I was also disappointed to see that Zimbra blocks Opera, my default browser (that works just fine with Gmail and RoundCube). I'll stop here. I'm fed up, I lost my time, I was expecting a whole lot more
Sorry if I got mad, but I think the Zimbra team needs to know customer feedback.