At Applied Trust we've been using the Zimbra Collaboration Suite for a few years now. Ned is our primary admin, and he probably has some criticisms based on his in-depth experience, but from my user perspective it has been great. A few highlights for me:
- I have a good sized mailbox - about 3GB with tens of thousands of individual messages - and our very simple server is plenty fast. Loading messages out of any folder is quick and painless. Searching is also very fast.
- The shared calendar features are spectacular. Setting up meetings with Exchange users is a cinch. Words like "August 3rd" or "Thursday" in the email window are highlighted, and holding the mouse over it shows upcoming meetings. My only complaint is that you can't seem to set the default calendar sharing rules for new users. When we hire new people, we need to both make our calendar viewable by them, and accept their calendar share. High maintenance.
- Similarly, contacts works great. Very little to say since it works so well.
- Integration with the iPhone is as good as for Exchange users. I have calendars, email and contacts on my phone with no problem.
On the infrastructure side, Ned probably has more to say, but we've done many upgrades and they all seem to have gone very smoothly. As an open source-based collaboration suite, Zimbra is a strong competitor Exchange. I'm happy. Ned, care to comment?